INVESTMENT SECURITIES - Summary of Investment Securities with Unrealized Losses (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value
Less Than 12 Months	$ 20,163	$ 878,890
12 Months or Longer	181,707	0
Total	201,870	878,890
Gross Unrealized Losses
Less Than 12 Months	(91)	(30,214)
12 Months or Longer	(1,433)	0
Total	(1,524)	(30,214)
Fair Value
Less Than 12 Months	271,241	698,170
12 Months or Longer	7,042	7,235
Total	278,283	705,405
Gross Unrealized Losses
Less Than 12 Months	(754)	(5,246)
12 Months or Longer	(139)	(124)
Total	(893)	(5,370)
Private label residential mortgage-backed securities
Fair Value
Less Than 12 Months	14,938	0
12 Months or Longer	290	403
Total	15,228	403
Gross Unrealized Losses
Less Than 12 Months	(116)	0
12 Months or Longer	(2)	(1)
Total	(118)	(1)
Corporate bonds
Fair Value
Less Than 12 Months		190,332
12 Months or Longer		0
Total		190,332
Gross Unrealized Losses
Less Than 12 Months		(20,946)
12 Months or Longer		0
Total		(20,946)
Fair Value
Less Than 12 Months	5,075	26,152
12 Months or Longer	5,075	0
Total	10,150	26,152
Gross Unrealized Losses
Less Than 12 Months	(97)	(505)
12 Months or Longer	(127)	0
Total	(224)	(505)
Collateralized loan obligations
Fair Value
Less Than 12 Months	10,001	411,207
12 Months or Longer	181,707	0
Total	191,708	411,207
Gross Unrealized Losses
Less Than 12 Months	(55)	(5,077)
12 Months or Longer	(1,433)	0
Total	(1,488)	(5,077)
Fair Value
Less Than 12 Months	114,191	72,204
12 Months or Longer	0	0
Total	114,191	72,204
Gross Unrealized Losses
Less Than 12 Months	(266)	(282)
12 Months or Longer	0	0
Total	(266)	(282)
Commercial mortgage-backed securities
Fair Value
Less Than 12 Months	10,162	277,351
12 Months or Longer	0	0
Total	10,162	277,351
Gross Unrealized Losses
Less Than 12 Months	(36)	(4,191)
12 Months or Longer	0	0
Total	(36)	(4,191)
Agency mortgage-backed securities
Fair Value
Less Than 12 Months	137,037	599,814
12 Months or Longer	1,677	6,832
Total	138,714	606,646
Gross Unrealized Losses
Less Than 12 Months	(275)	(4,459)
12 Months or Longer	(10)	(123)
Total	$ (285)	$ (4,582)