Label	Element	Value
Pension Plan [Member]
Defined Benefit Plan Benefit Obligation	us-gaap_DefinedBenefitPlanBenefitObligation	$ 107,571,000
Defined Benefit Plan, Fair Value of Plan Assets	us-gaap_DefinedBenefitPlanFairValueOfPlanAssets	104,522,000
Other Postretirement Benefit Plans Defined Benefit [Member]
Defined Benefit Plan Benefit Obligation	us-gaap_DefinedBenefitPlanBenefitObligation	235,000
Defined Benefit Plan, Fair Value of Plan Assets	us-gaap_DefinedBenefitPlanFairValueOfPlanAssets	0
Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member] | Retained Earnings [Member]
Stockholders Equity After New Accounting Principle In Period Of Adoption	fbp_StockholdersEquityAfterNewAccountingPrincipleInPeriodOfAdoption	$ 1,159,495,000