LOANS HELD FOR INVESTMENT - Breakdown Between Accrual and Nonaccrual Status of TDRs (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
TDR [Member]
Financing Receivable Modifications [Line Items]
Financing receivable modifications recorded investment of loan forced to nonaccrual status	$ 9.1	$ 14.8

Amount represents loans that are performing under the terms of the restructuring agreement but are reported in nonacrrual status until the restructured loans meet the criteria of sustained payment performance.

No definition available.

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