FIRST BANCORP. (Holding Company Only) Financial Information - Statements of Financial Condition (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
ASSETS
Cash and due from banks	$ 813,732	$ 532,985
Money market investments	213,093	219,473	$ 216,965
Investment securities available for sale, at market:
Other investment securities	1,110,952	1,092,833
Carrying Value Of Other Equity Security	1,000	900
Loans Receivable, net	8,931,085	9,069,024
Other assets	472,965	476,459
Total assets	12,714,370	12,573,019
Liabilities:
Other borrowings	216,183	226,492
Accounts payable and other liabilities	159,240	159,269
Total liabilities	10,965,203	10,878,885
Stockholders Equity	1,749,167	1,694,134	$ 1,705,750
Total liabilities and stockholders' equity	12,714,370	12,573,019
Holding Company [Member]
ASSETS
Cash and due from banks	28,470	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	256	266
Other assets	5,370	4,632
Total assets	1,995,267	1,949,610
Liabilities:
Other borrowings	216,183	226,492
Accounts payable and other liabilities	29,917	28,984
Total liabilities	246,100	255,476
Stockholders Equity	1,749,167	1,694,134
Total liabilities and stockholders' equity	1,995,267	1,949,610
Holding Company [Member] | Investment In Banking Subsidiary [Member]
Investment securities available for sale, at market:
Equity Method Investments	1,939,272	1,888,036
Holding Company [Member] | Non Banking Subsidiary [Member]
Investment securities available for sale, at market:
Equity Method Investments	9,017	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	$ 3,557	$ 3,866