INVESTMENT SECURITIES - Summary of Amortized Cost and Fair Value (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Securities held-to-maturity:
Amortized Cost	$ 863,269	$ 884,234
Gross Unrealized Gains	18,093	17,442
Gross Unrealized Losses	(1,464)	(1,933)
Fair Value	879,898	899,743
Securities available-for-sale:
Amortized Cost	2,451,151	2,396,968
Gross Unrealized Gains	12,717	12,958
Gross Unrealized Losses	(29,327)	(28,438)
Fair Value	2,434,541	2,381,488
SBA loan pool securities
Securities available-for-sale:
Amortized Cost	1,138	1,221
Gross Unrealized Gains	7	0
Gross Unrealized Losses	0	0
Fair Value	1,145	1,221
Private label residential mortgage-backed securities
Securities available-for-sale:
Amortized Cost	121,214	121,397
Gross Unrealized Gains	16	18
Gross Unrealized Losses	(4,473)	(4,238)
Fair Value	116,757	117,177
Corporate bonds
Securities available-for-sale:
Amortized Cost	19,134	48,574
Gross Unrealized Gains	105	482
Gross Unrealized Losses	(95)	(108)
Fair Value	19,144	48,948
Collateralized loan obligations
Securities available-for-sale:
Amortized Cost	1,489,865	1,395,094
Gross Unrealized Gains	12,581	12,449
Gross Unrealized Losses	(193)	(674)
Fair Value	1,502,253	1,406,869
Agency mortgage-backed securities
Securities available-for-sale:
Amortized Cost	819,800	830,682
Gross Unrealized Gains	8	9
Gross Unrealized Losses	(24,566)	(23,418)
Fair Value	795,242	807,273
Corporate bonds
Securities held-to-maturity:
Amortized Cost	240,304	240,090
Gross Unrealized Gains	13,722	13,032
Gross Unrealized Losses	0	(91)
Fair Value	254,026	253,031
Collateralized loan obligations
Securities held-to-maturity:
Amortized Cost	317,223	338,226
Gross Unrealized Gains	1,484	1,461
Gross Unrealized Losses	(70)	(61)
Fair Value	318,637	339,626
Commercial mortgage-backed securities
Securities held-to-maturity:
Amortized Cost	305,742	305,918
Gross Unrealized Gains	2,887	2,949
Gross Unrealized Losses	(1,394)	(1,781)
Fair Value	$ 307,235	$ 307,086

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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