LOANS HELD FOR INVESTMENT - Corporation's Aging of Loans Held for Investment Portfolio (Parenthetical) (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 11,298,618	$ 11,060,658
Nonaccrual Loans with No ACL	33,211	27,733
Loans Past Due 90 days or more and Still Accruing	81,645	114,679
Nonaccrual	97,516	110,717
Total TDR loans	387,700
Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Total TDR loans	340,100	363,400
PCD loans [Member]
Financing Receivable, Past Due [Line Items]
Loans Past Due 90 days or more and Still Accruing	12,800	20,600
Florida region [Member}
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,050,620	1,946,740
Nonaccrual	6,500	8,200
30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	64,689	44,202
Residential Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,830,974	2,978,895
Residential Portfolio Segment [Member] \| Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,787,938	2,923,768
Residential Portfolio Segment [Member] \| Florida region [Member}
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	415,742	429,322
Residential Portfolio Segment [Member] \| Florida region [Member} \| Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	410,224	422,170
Residential Portfolio Segment [Member] \| Conventional residential mortgage loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,712,011	2,853,503
Nonaccrual Loans with No ACL	3,412	3,689
Loans Past Due 90 days or more and Still Accruing	18,066	28,433
Nonaccrual	43,036	55,127
Residential Portfolio Segment [Member] \| Conventional residential mortgage loans [Member] \| Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,668,975	2,798,376
Residential Portfolio Segment [Member] \| Conventional residential mortgage loans [Member] \| PCD loans [Member]
Financing Receivable, Past Due [Line Items]
Loans Past Due 90 days or more and Still Accruing	11,800	19,100
Residential Portfolio Segment [Member] \| Conventional residential mortgage loans [Member] \| Florida region [Member}
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	414,996	428,582
Residential Portfolio Segment [Member] \| Conventional residential mortgage loans [Member] \| Florida region [Member} \| Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	409,478	421,430
Residential Portfolio Segment [Member] \| Conventional residential mortgage loans [Member] \| 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Residential Portfolio Segment [Member] \| Conventional residential mortgage loans [Member] \| Less Than Two Payments In Arrears [Member] \| 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	71,700	66,000
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	118,963	125,392
Nonaccrual Loans with No ACL	0	0
Loans Past Due 90 days or more and Still Accruing	49,044	65,515
Nonaccrual	0	0
Total TDR loans	54,800	57,600
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member] \| Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	118,963	125,392
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member] \| Florida region [Member}
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	746	740
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member] \| Florida region [Member} \| Performing Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	746	740
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member] \| 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	0	0
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member] \| Past Due, 15 Months Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loans Past Due 90 days or more and Still Accruing	31,000	46,600
Residential Portfolio Segment [Member] \| FHA/VA government-guaranteed loans [Member] \| Less Than Two Payments In Arrears [Member] \| 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	6,000	6,100
Residential Portfolio Segment [Member] \| GNMA [Member] \| Repurchase Option Program [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	8,100	7,200
Loans Past Due 90 days or more and Still Accruing	8,000	7,200
Commercial Portfolio Segment [Member] \| Commercial And Industrial Sector [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,858,286	2,887,251
Nonaccrual Loans with No ACL	10,854	11,393
Loans Past Due 90 days or more and Still Accruing	9,089	7,827
Nonaccrual	15,715	17,135
Commercial Portfolio Segment [Member] \| Florida region [Member} \| Commercial And Industrial Sector [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,016,120	940,654
Nonaccrual Loans with No ACL	600	500
Commercial Portfolio Segment [Member] \| 30-59 Days Past Due [Member] \| Commercial And Industrial Sector [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	4,463	2,047
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	2,265,614	2,167,469
Nonaccrual Loans with No ACL	15,699	8,289
Loans Past Due 90 days or more and Still Accruing	1,461	9,919
Nonaccrual	23,741	25,337
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member] \| PCD loans [Member]
Financing Receivable, Past Due [Line Items]
Loans Past Due 90 days or more and Still Accruing	1,000	1,500
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member] \| Florida region [Member}
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	511,167	465,238
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member] \| 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	1,415	2,402
Commercial Portfolio Segment [Member] \| Less Than Two Payments In Arrears [Member] \| Mortgage Receivable [Member] \| 30-59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 1,900	$ 700

Amount of financing receivable modified as troubled debt restructuring.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953676-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=121585226&loc=d3e18845-111554

+ Details

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

- Definition

Amortized cost of financing receivable on nonaccrual status with no allowance for credit loss. Excludes net investment in lease.

+ References

+ Details

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

- Definition

Amortized cost of financing receivable 90 days or more past due and still accruing. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919258-210447

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=d3e5111-111524

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 80
-URI https://asc.fasb.org/extlink&oid=124267575&loc=SL82922355-210448

+ Details

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

- Definition

Amortized cost of financing receivable on nonaccrual status. Excludes net investment in lease.

+ 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 (a)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=d3e5111-111524

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919258-210447

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (3)

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (2)

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
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

Amortized cost, before allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI https://asc.fasb.org/extlink&oid=123577603&loc=SL6953401-111524

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 79
-URI https://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3)(b))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 14
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919253-210447

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919230-210447

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 80
-URI https://asc.fasb.org/extlink&oid=124267575&loc=SL82922355-210448

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (1)

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (2)

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1404
-Paragraph (a)

+ Details

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

- Details

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

- Details

Name:	us-gaap_CreditLossStatusAxis=us-gaap_FinancialAssetAcquiredWithCreditDeteriorationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=country_US
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_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateLoanTypeAxis=us-gaap_ConventionalLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fbp_LessThanTwoPaymentsInArrearsMember
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_FinancingReceivablesPeriodPastDueAxis=fbp_PastDue15MonthsDelinquentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_QualitativeAndQuantitativeInformationTransferorsContinuingInvolvementTransferredFinancialAssetsByTransferOrTransfereeAxis=fbp_RepurchaseOptionProgramMember
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_EquitySecuritiesByIndustryAxis=us-gaap_CommercialAndIndustrialSectorMember
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: