LOAN PORTFOLIO - Breakdown Between Accrual and Nonaccrual Status of TDRs (Parenthetical) (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
TDR [Member]
Financing Receivable Modifications [Line Items]
Loans forced to nonaccrual status	$ 25.5	$ 17.7

Amount represents nonaccrual loans that are performing under the terms of the restructuring agreement but are reported in nonaccrual status until the restructured loans meet the specific requirements.

No definition available.

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