INVESTMENT SECURITIES - Summary of Amortized Cost and Fair Value (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Securities held-to-maturity:
Amortized Cost	$ 962,262	$ 962,203
Gross Unrealized Gains	5,706	296
Gross Unrealized Losses	(19,510)	(30,214)
Fair Value	948,458	932,285
Securities available-for-sale:
Amortized Cost	1,658,863	838,768
Gross Unrealized Gains	7,570	198
Gross Unrealized Losses	(2,722)	(5,370)
Fair Value	1,663,711	833,596
SBA loan pool securities
Securities available-for-sale:
Amortized Cost	1,363	1,485
Gross Unrealized Gains	45	19
Gross Unrealized Losses	0	0
Fair Value	1,408	1,504
Private label residential mortgage-backed securities
Securities available-for-sale:
Amortized Cost	1,596	1,755
Gross Unrealized Gains	3	14
Gross Unrealized Losses	(4)	(1)
Fair Value	1,595	1,768
Corporate bonds
Securities available-for-sale:
Amortized Cost	26,653	26,657
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(476)	(505)
Fair Value	26,177	26,152
Collateralized loan obligations
Securities available-for-sale:
Amortized Cost	966,920	111,719
Gross Unrealized Gains	1,345	31
Gross Unrealized Losses	(1,944)	(282)
Fair Value	966,321	111,468
Agency mortgage-backed securities
Securities available-for-sale:
Amortized Cost	662,331	697,152
Gross Unrealized Gains	6,177	134
Gross Unrealized Losses	(298)	(4,582)
Fair Value	668,210	692,704
Corporate bonds
Securities held-to-maturity:
Amortized Cost	239,479	239,274
Gross Unrealized Gains	1,518	255
Gross Unrealized Losses	(9,292)	(20,946)
Fair Value	231,705	218,583
Collateralized loan obligations
Securities held-to-maturity:
Amortized Cost	416,315	416,284
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(7,950)	(5,077)
Fair Value	408,365	411,207
Commercial mortgage-backed securities
Securities held-to-maturity:
Amortized Cost	306,468	306,645
Gross Unrealized Gains	4,188	41
Gross Unrealized Losses	(2,268)	(4,191)
Fair Value	$ 308,388	$ 302,495

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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