FIRST BANCORP. (Holding Company Only) Financial Information - Statements of Loss (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income:
Interest income on investment securities	$ 12,109,000	$ 11,894,000	$ 39,361,000	$ 40,065,000
Other Interest And Dividend Income	1,293,000	662,000	2,504,000	3,006,000
Expense:
Impairement on equity securities	0	6,096,000	371,000	6,104,000
Gains Losses On Extinguishment Of Debt	1,391,000	0	1,391,000	4,217,000
Segment income	7,122,000	59,419,000	112,888,000	166,376,000
Income tax benefit (expense)	8,398,000	(10,444,000)	7,181,000	(23,690,000)
Net (loss) income	(10,752,000)	24,074,000	42,787,000	69,371,000
Other comprehensive income, net of tax	3,719,000	(12,157,000)	23,480,000	32,109,000
Comprehensive (loss) income	(7,033,000)	11,917,000	66,267,000	101,480,000
Holding Company [Member]
Income:
Other Interest And Dividend Income	5,000	5,000	15,000	15,000
Other income	68,000	58,000	195,000	181,000
Total interest income	4,873,000	1,885,000	8,610,000	40,176,000
Expense:
Notes payable and other borrowings	2,139,000	1,817,000	6,166,000	5,777,000
Other operating expenses	814,000	685,000	2,480,000	2,313,000
Total operating expenses	2,953,000	2,502,000	8,646,000	8,090,000
Gains Losses On Extinguishment Of Debt	1,391,000	0	1,391,000	4,217,000
Segment income	3,311,000	(617,000)	1,355,000	36,303,000
Income tax benefit (expense)	(45,000)	0	(45,000)	0
Equity in undistributed earnings (losses) of subsidiaries	(14,018,000)	24,691,000	41,477,000	33,068,000
Net (loss) income	(10,752,000)	24,074,000	42,787,000	69,371,000
Other comprehensive income, net of tax	3,719,000	(12,157,000)	23,480,000	32,109,000
Comprehensive (loss) income	(7,033,000)	11,917,000	66,267,000	101,480,000
Investment In Banking Subsidiary [Member] | Holding Company [Member]
Income:
Dividend Income From Subsidiaries	1,800,000	1,822,000	5,400,000	32,980,000
Non Banking Subsidiary [Member] | Holding Company [Member]
Income:
Dividend Income From Subsidiaries	$ 3,000,000	$ 0	$ 3,000,000	$ 7,000,000