XML 17 R55.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Allowance for Loan and Lease Losses (Note Restructurings During Period) (Details) (USD $) In Thousands, unless otherwise specified | 3 Months Ended
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Mar. 31, 2015 loans | Mar. 31, 2014 loans
Non-PCI Loans |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 59 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember | 61 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | $ 11,718 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember | $ 13,063 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 8 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember | 9 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 4,941 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember | 1,315 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember
Non-PCI Loans | Interest Only Loan |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 1 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 7 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 3,796 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 2,253 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 1 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 2 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 3,796 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 410 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Non-PCI Loans | Loan Term Extension |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 6 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 12 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 770 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 3,192 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 1 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 1 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 220 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 41 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Non-PCI Loans | Below Market Interest Rate |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 45 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 28 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 6,866 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 5,598 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 4 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 4 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 778 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 576 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Non-PCI Loans | Discharge of Debt |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 7 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 14 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 286 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 2,020 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 2 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 2 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 147 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 288 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Non-PCI Loans | Commercial | Interest Only Loan | Mortgage |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 4 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 1,911 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 2 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 410 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Non-PCI Loans | Commercial | Interest Only Loan | Commercial and industrial |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 1 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 1 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 3,796 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 196 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 1 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 3,796 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Non-PCI Loans | Commercial | Interest Only Loan | Lease financing |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_FinanceLeasesFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 2 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_FinanceLeasesFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_FinanceLeasesFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 146 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_FinanceLeasesFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_FinanceLeasesFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_FinanceLeasesFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_FinanceLeasesFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_FinanceLeasesFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Non-PCI Loans | Commercial | Loan Term Extension | Construction and land development |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 1 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 220 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 1 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 220 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Non-PCI Loans | Commercial | Loan Term Extension | Mortgage |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 3 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 5 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 535 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 2,620 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Non-PCI Loans | Commercial | Loan Term Extension | Lease financing |  |
Financing Receivable, Modifications [Line Items] |  |
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Financing Receivable, Modifications, Post-Modification Recorded Investment | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_FinanceLeasesFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 234 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_FinanceLeasesFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_FinanceLeasesFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_FinanceLeasesFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_FinanceLeasesFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_FinanceLeasesFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Non-PCI Loans | Commercial | Below Market Interest Rate | Construction and land development |  |
Financing Receivable, Modifications [Line Items] |  |
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Financing Receivable, Modifications, Post-Modification Recorded Investment | 47 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 82 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Non-PCI Loans | Commercial | Below Market Interest Rate | Mortgage |  |
Financing Receivable, Modifications [Line Items] |  |
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Financing Receivable, Modifications, Post-Modification Recorded Investment | 3,541 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 4,677 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 2 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 1 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 733 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 449 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Non-PCI Loans | Commercial | Below Market Interest Rate | Commercial and industrial |  |
Financing Receivable, Modifications [Line Items] |  |
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Financing Receivable, Modifications, Post-Modification Recorded Investment | 172 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 110 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Non-PCI Loans | Commercial | Discharge of Debt | Mortgage |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 1 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 1,003 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Non-PCI Loans | Noncommerical | Loan Term Extension | Mortgage |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 5 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 338 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Non-PCI Loans | Noncommerical | Loan Term Extension | Revolving mortgage |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 1 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 10 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember |
Non-PCI Loans | Noncommerical | Loan Term Extension | Consumer |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 1 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 5 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 1 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 41 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Non-PCI Loans | Noncommerical | Below Market Interest Rate | Mortgage |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 23 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 8 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 708 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 451 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 2 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 3 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 45 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 127 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Non-PCI Loans | Noncommerical | Below Market Interest Rate | Construction and land development |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 2 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_ConstructionAndLandDevelopmentNoncommercialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_ConstructionAndLandDevelopmentNoncommercialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 396 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_ConstructionAndLandDevelopmentNoncommercialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_ConstructionAndLandDevelopmentNoncommercialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_ConstructionAndLandDevelopmentNoncommercialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_ConstructionAndLandDevelopmentNoncommercialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_ConstructionAndLandDevelopmentNoncommercialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_ConstructionAndLandDevelopmentNoncommercialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Non-PCI Loans | Noncommerical | Below Market Interest Rate | Revolving mortgage |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 2 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 5 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 18 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 278 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Non-PCI Loans | Noncommerical | Below Market Interest Rate | Consumer |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 3 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 34 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Non-PCI Loans | Noncommerical | Below Market Interest Rate | Other |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 1 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_OtherLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_OtherLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 1,950 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_OtherLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_OtherLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_OtherLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_OtherLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_OtherLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_OtherLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Non-PCI Loans | Noncommerical | Discharge of Debt | Mortgage |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 2 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 7 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 68 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 708 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 2 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 288 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Non-PCI Loans | Noncommerical | Discharge of Debt | Construction and land development |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_ConstructionAndLandDevelopmentNoncommercialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 1 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_ConstructionAndLandDevelopmentNoncommercialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_ConstructionAndLandDevelopmentNoncommercialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 62 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_ConstructionAndLandDevelopmentNoncommercialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_ConstructionAndLandDevelopmentNoncommercialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_ConstructionAndLandDevelopmentNoncommercialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_ConstructionAndLandDevelopmentNoncommercialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_ConstructionAndLandDevelopmentNoncommercialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Non-PCI Loans | Noncommerical | Discharge of Debt | Revolving mortgage |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 5 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 4 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 218 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 229 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 2 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 147 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Non-PCI Loans | Noncommerical | Discharge of Debt | Consumer |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 1 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 18 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_NonPCILoansMember / fcnca_LoanTermAxis = us-gaap_DischargeOfDebtMember
PCI Loans |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 7 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember | 9 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 470 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember | 21,765 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 1 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember | 4 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 65 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember | 47,718 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember
PCI Loans | Interest Only Loan |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 2 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 15,906 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 2 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 15,906 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
PCI Loans | Loan Term Extension |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 1 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 281 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
PCI Loans | Below Market Interest Rate |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 7 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 6 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 470 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 5,578 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 1 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 2 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 65 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 31,812 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
PCI Loans | Commercial | Interest Only Loan | Mortgage |  |
Financing Receivable, Modifications [Line Items] |  |
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Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember | 15,906 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_InterestOnlyLoanMember
PCI Loans | Commercial | Loan Term Extension | Construction and land development |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 1 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 281 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_LoanTermExtensionMember
PCI Loans | Commercial | Below Market Interest Rate | Construction and land development |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 1 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 37 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CommercialRealEstateConstructionFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
PCI Loans | Commercial | Below Market Interest Rate | Mortgage |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 4 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 5,439 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 1 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 47 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
PCI Loans | Commercial | Below Market Interest Rate | Commercial and industrial |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 1 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | 65 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = fcnca_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialPortfolioSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
PCI Loans | Noncommerical | Below Market Interest Rate | Mortgage |  |
Financing Receivable, Modifications [Line Items] |  |
Financing Receivable, Modifications, Number of Contracts | 7 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 1 us-gaap_FinancingReceivableModificationsNumberOfContracts2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Post-Modification Recorded Investment | 470 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 102 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | 1 us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | $ 0 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember | $ 436 us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1 / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_MortgageReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fcnca_NoncommercialSegmentMember / fcnca_LoanDesignationAxis = fcnca_LoansAcquiredWithDeterioratedCreditQualityMember / fcnca_LoanTermAxis = fcnca_BelowMarketInterestRateMember

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