LOAN PORTFOLIO - Loan Modifications Considered Troubled Debt Restructurings Defaulted (Detail) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2016 USD ($) numberofcontracts	Sep. 30, 2015 USD ($) numberofcontracts	Sep. 30, 2016 USD ($) numberofcontracts	Sep. 30, 2015 USD ($) numberofcontracts
Financing Receivable Modifications [Line Items]
Number of Contracts \| numberofcontracts	42	78	171	209
Recorded Investment \| $	$ 1,898	$ 4,118	$ 5,947	$ 14,215
Non Fha Va Residential Mortgage Loans [Member]
Financing Receivable Modifications [Line Items]
Number of Contracts \| numberofcontracts	14	23	35	50
Recorded Investment \| $	$ 1,707	$ 3,744	$ 4,863	$ 7,646
Commercial And Industrial Loan [Member]
Financing Receivable Modifications [Line Items]
Number of Contracts \| numberofcontracts			0	4
Recorded Investment \| $			$ 0	$ 5,745
Consumer Auto Loans [Member]
Financing Receivable Modifications [Line Items]
Number of Contracts \| numberofcontracts	5	1	45	8
Recorded Investment \| $	$ 68	$ 10	$ 702	$ 50
Other Consumer Loans [Member]
Financing Receivable Modifications [Line Items]
Number of Contracts \| numberofcontracts	22	51	89	141
Recorded Investment \| $	$ 93	$ 219	$ 339	$ 589
Finance Leases [Member]
Financing Receivable Modifications [Line Items]
Number of Contracts \| numberofcontracts	1	3	2	6
Recorded Investment \| $	$ 30	$ 145	$ 43	$ 185

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.

No definition available.

+ Details

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

- Definition

Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953682-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a payment default.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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