FIRST BANCORP. (Holding Company Only) Financial Information - Statements of Financial Condition (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
ASSETS
Cash and due from banks	$ 518,835	$ 532,985
Money market investments	10,108	219,473	$ 219,486
Investment securities available for sale, at market:
Other investment securities	1,182,299	1,092,833
Carrying Value Of Other Equity Security	2,100	900
Loans Receivable, net	8,706,363	8,907,541
Other assets	476,094	476,459
Total assets	12,075,253	12,573,019
Liabilities:
Other borrowings	216,187	226,492
Accounts payable and other liabilities	122,867	159,269
Total liabilities	10,275,367	10,878,885
Stockholders Equity	1,799,886	1,694,134	$ 1,700,950
Total liabilities and stockholders' equity	12,075,253	12,573,019
Holding Company [Member]
ASSETS
Cash and due from banks	29,074	29,103
Money market investments	6,111	6,111
Investment securities available for sale, at market:
Carrying Value Of Other Equity Security	285	285
Loans Receivable, net	236	266
Other assets	4,354	4,632
Total assets	2,016,631	1,949,610
Liabilities:
Other borrowings	216,187	226,492
Accounts payable and other liabilities	558	28,984
Total liabilities	216,745	255,476
Stockholders Equity	1,799,886	1,694,134
Total liabilities and stockholders' equity	2,016,631	1,949,610
Holding Company [Member] | Investment In Banking Subsidiary [Member]
Investment securities available for sale, at market:
Equity Method Investments	1,960,090	1,888,036
Holding Company [Member] | Non Banking Subsidiary [Member]
Investment securities available for sale, at market:
Equity Method Investments	9,991	14,382
Holding Company [Member] | Statutory Trust One [Member]
Investment securities available for sale, at market:
Equity Method Investments	2,929	2,929
Holding Company [Member] | Statutory Trust Two [Member]
Investment securities available for sale, at market:
Equity Method Investments	$ 3,561	$ 3,866