XML 130 R114.htm IDEA: XBRL DOCUMENT
v3.24.0.1

Mortgage Servicing Rights - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Transfers and Servicing [Abstract] |  |  |
Financing receivables serviced for third parties | $ 3,450 | $ 3,690 |
Contractually specified servicing fee, late fee, and ancillary fee earned in exchange for servicing financial asset | $ 9 | $ 10 | $ 9

X
- Definition Financing Receivables Serviced For Third Parties + References No definition available. + Details
Name: | fcnca_FinancingReceivablesServicedForThirdParties
Namespace Prefix: | fcnca_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of contractually specified servicing fee, late fee, and ancillary fee recognized as income for servicing asset and servicing liability. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 860 -SubTopic 50 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481229/860-50-50-2 + Details
Name: | us-gaap_ContractuallySpecifiedServicingFeesLateFeesAndAncillaryFeesEarnedInExchangeForServicingFinancialAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_TransfersAndServicingAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration