Delinquent rebooked delinquent GNMA loans eligible for repurchase.

No definition available.

Name:	fbp_Defaultedloanscollateralizingsecurities
Namespace Prefix:	fbp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Threshold period for when financing receivable is considered past due to write off as uncollectible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	fbp_FinancingReceivableThresholdPeriodPastDueWriteoff
Namespace Prefix:	fbp_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of residential mortgage loan that are no longer accruing interest.

+ References

No definition available.

+ Details

Name:	fbp_PeriodOfResidentialMortgageLoanThatAreNoLongerAccruingInterest
Namespace Prefix:	fbp_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Recorded investment in financing receivables that are 90 days or more past due and still accruing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5111-111524

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

+ Details

Name:	us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Describes the policies and procedures for identifying and measuring losses on loans when the present value of expected cash flows discounted at the loan's effective interest rate, or, alternatively, a loan's observable market price or fair value of the underlying collateral is less than the carrying amount of the loan, and sets forth the amount of the loss. Also sets forth material facts pertaining to significant loan modifications in a troubled debt restructuring, describes the method for valuing a loan deemed to be impaired or nonperforming, indicates whether income on impaired or nonperforming loans are being recognized and describes the method for recognizing the income.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 35
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=109220201&loc=d3e2555-111518

+ Details

Name:	us-gaap_LoansAndLeasesReceivableImpairedDescription
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fbp_OtherloansmemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivables30To59DaysPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=us-gaap_MortgageReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConstructionLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ResidentialMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CommercialLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_LandMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_CreditCardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoansInsuredOrGuaranteedByGovernmentAuthoritiesAxis=us-gaap_LoansInsuredOrGuaranteedByUsGovernmentAuthoritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentPerformanceStatusAxis=fbp_NonaccrualOfInterestMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

LOAN PORTFOLIO - Corporation's Aging of Loans Held for Investment Portfolio (Parenthetical) (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Financing Receivable, Past Due [Line Items]
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing	$ 114,744	$ 129,083
Loans and Leases Receivable, Gross	9,113,955	8,858,123	$ 8,640,291
Residential Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans and Leases Receivable, Gross	3,070,746	3,163,208	3,238,001
Residential Portfolio Segment [Member] \| Other Loans Member [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing	$ 16,607	14,564
Loans and Leases Receivable, Impaired, Description	According to the Corporation's delinquency policy and consistent with the instructions for the preparation of the Consolidated Financial Statements for Bank Holding Companies (FR Y-9C) required by the Federal Reserve Board, residential mortgage, commercial mortgage, and construction loans are considered past due when the borrower is in arrears on two or more monthly payments.
Loans and Leases Receivable, Gross	$ 2,937,846	3,016,003
Residential Portfolio Segment [Member] \| Financing Receivables 30 To 59 Days Past Due [Member] \| Other Loans Member [Member]
Financing Receivable, Past Due [Line Items]
Loans and Leases Receivable, Gross	110,100	101,400
Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans and Leases Receivable, Gross	3,930,293	3,750,202
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing	$ 3,604	946
Loans and Leases Receivable, Impaired, Description	According to the Corporation's delinquency policy and consistent with the instructions for the preparation of the Consolidated Financial Statements for Bank Holding Companies (FR Y-9C) required by the Federal Reserve Board, residential mortgage, commercial mortgage, and construction loans are considered past due when the borrower is in arrears on two or more monthly payments.
Loans and Leases Receivable, Gross	$ 1,550,364	1,522,662	1,533,308
Commercial Portfolio Segment [Member] \| Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Loans and Leases Receivable, Gross	100,244	79,429	84,683
Commercial Portfolio Segment [Member] \| Construction Loans [Member] \| Residential Mortgage [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing	0	0
Loans and Leases Receivable, Gross	12,128	11,151
Commercial Portfolio Segment [Member] \| Construction Loans [Member] \| Commercial Loan [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing	0	0
Loans and Leases Receivable, Gross	68,936	47,965
Commercial Portfolio Segment [Member] \| Construction Loans [Member] \| Land [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing	$ 222	67
Loans and Leases Receivable, Impaired, Description	According to the Corporation's delinquency policy and consistent with the instructions for the preparation of the Consolidated Financial Statements for Bank Holding Companies (FR Y-9C) required by the Federal Reserve Board, residential mortgage, commercial mortgage, and construction loans are considered past due when the borrower is in arrears on two or more monthly payments.
Loans and Leases Receivable, Gross	$ 19,180	20,313
Commercial Portfolio Segment [Member] \| Financing Receivables 30 To 59 Days Past Due [Member] \| Mortgage Receivable [Member]
Financing Receivable, Past Due [Line Items]
Loans and Leases Receivable, Gross	19,400	5,100
Commercial Portfolio Segment [Member] \| Financing Receivables 30 To 59 Days Past Due [Member] \| Construction Loans [Member] \| Land [Member]
Financing Receivable, Past Due [Line Items]
Loans and Leases Receivable, Gross	100	200
Consumer Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Loans and Leases Receivable, Gross	$ 2,112,916	1,944,713	$ 1,775,250
Consumer Portfolio Segment [Member] \| Credit Card [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Threshold Period Past Due, Writeoff	180 days
Consumer Portfolio Segment [Member] \| Other Loans Member [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing	$ 3,305	3,752
Loans and Leases Receivable, Gross	706,913	664,701
Loans Insured or Guaranteed by US Government Authorities [Member] \| Residential Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing	89,687	104,751
Defaulted Loans Collateralizing Securities	$ 41,900	43,600
Loans and Leases Receivable, Impaired, Description	According to the Corporation's delinquency policy and consistent with the instructions for the preparation of the Consolidated Financial Statements for Bank Holding Companies (FR Y-9C) required by the Federal Reserve Board, residential mortgage, commercial mortgage, and construction loans are considered past due when the borrower is in arrears on two or more monthly payments.
Loans and Leases Receivable, Gross	$ 132,900	147,205
Loans Insured or Guaranteed by US Government Authorities [Member] \| Residential Portfolio Segment [Member] \| Financing Receivables 30 To 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Loans and Leases Receivable, Gross	6,000	5,600
Loans Insured or Guaranteed by US Government Authorities [Member] \| Nonaccrual Of Interest [Member] \| Residential Portfolio Segment [Member] \| Financing Receivables 30 To 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable Recorded Investment 90 Days Past Due And Still Accruing	$ 39,800	$ 51,400
Period Of Residential Mortgage Loan That Are No Longer Accruing Interest	15 months	15 months