NATURE OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Securities purchased and sold under agreements to repurchase (Detail)	12 Months Ended
Dec. 31, 2018
Accounting Policies [Abstract]
Modified Repurchase Agreements Threshold	10.00%

The percentage difference between the cash flows under the terms of the modified repurchase agreement and the present value of the remaining cash flows under the terms of the original instrument.

No definition available.

Name:	fbp_ModifiedRepurchaseAgreementsThreshold
Namespace Prefix:	fbp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration