LOAN PORTFOLIO - Loan Portfolio Held for Investment (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Financial Information [Line Items]
Commercian Loans Collaterized By Real Estate	$ 884.0	$ 853.9

Commercial loans secured by real estate (owner-occupied commercial loans secured by real estate) but are not dependent upon real estate for repayment.

No definition available.

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