INVESTMENT SECURITIES (Details 2) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value
Less Than 12 Months	$ 772,669	$ 2,527,519
12 Months or More	233,470	228,733
Total	1,006,139	2,756,252
Gross Unrealized Losses
Less Than 12 Months	(5,844)	(16,075)
12 Months or More	(3,802)	(6,272)
Total	(9,646)	(22,347)
Fair Value
Less Than 12 Months	926,965
12 Months or More	233,470
Total	1,160,435
Gross Unrealized Losses
Less Than 12 Months	(6,009)
12 Months or More	(3,802)
Total	(9,811)
U.S. Treasury securities
Fair Value
Less Than 12 Months	30,375	907,400
12 Months or More	0	20,282
Total	30,375	927,682
Gross Unrealized Losses
Less Than 12 Months	(11)	(4,250)
12 Months or More	0	(142)
Total	(11)	(4,392)
U.S. government agency and U.S. government sponsored enterprise debt securities
Fair Value
Less Than 12 Months	35,019	541,385
12 Months or More	0	0
Total	35,019	541,385
Gross Unrealized Losses
Less Than 12 Months	(41)	(2,994)
12 Months or More	0	0
Total	(41)	(2,994)
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Fair Value
Less Than 12 Months	61,708	252,340
12 Months or More	59,680	20,793
Total	121,388	273,133
Gross Unrealized Losses
Less Than 12 Months	(716)	(2,562)
12 Months or More	(743)	(462)
Total	(1,459)	(3,024)
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Fair Value
Less Than 12 Months	304,826	535,842
12 Months or More	70,557	58,315
Total	375,383	594,157
Gross Unrealized Losses
Less Than 12 Months	(1,658)	(4,530)
12 Months or More	(795)	(1,871)
Total	(2,453)	(6,401)
Municipal securities
Fair Value
Less Than 12 Months	5,334	48,495
12 Months or More	2,870	14,739
Total	8,204	63,234
Gross Unrealized Losses
Less Than 12 Months	(111)	(437)
12 Months or More	(27)	(356)
Total	(138)	(793)
Non-agency residential mortgage-backed securities | Investment grade
Fair Value
Less Than 12 Months	7,027	5,123
12 Months or More	0	6,242
Total	7,027	11,365
Gross Unrealized Losses
Less Than 12 Months	(17)	(1)
12 Months or More	0	(172)
Total	(17)	(173)
Corporate debt securities | Investment grade
Fair Value
Less Than 12 Months	49,377	149,358
12 Months or More	81,935	80,276
Total	131,312	229,634
Gross Unrealized Losses
Less Than 12 Months	(178)	(683)
12 Months or More	(474)	(864)
Total	(652)	(1,547)
Corporate debt securities | Non-investment grade
Fair Value
Less Than 12 Months	0	0
12 Months or More	8,778	9,642
Total	8,778	9,642
Gross Unrealized Losses
Less Than 12 Months	0	0
12 Months or More	(1,413)	(1,849)
Total	(1,413)	(1,849)
Foreign bonds | Investment grade
Fair Value
Less Than 12 Months	276,313	74,101
12 Months or More	9,650	9,713
Total	285,963	83,814
Gross Unrealized Losses
Less Than 12 Months	(3,109)	(506)
12 Months or More	(350)	(288)
Total	(3,459)	(794)
Other securities
Fair Value
Less Than 12 Months	2,690	13,475
12 Months or More	0	8,731
Total	2,690	22,206
Gross Unrealized Losses
Less Than 12 Months	(3)	(112)
12 Months or More	0	(268)
Total	(3)	$ (380)
Non-agency commercial mortgage-backed security
Fair Value
Less Than 12 Months	154,296
12 Months or More	0
Total	154,296
Gross Unrealized Losses
Less Than 12 Months	(165)
12 Months or More	0
Total	$ (165)