AVAILABLE-FOR-SALE INVESTMENT SECURITIES (Details 4) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value
Less Than 12 Months	$ 434,038	$ 414,390
12 Months or More	241,519	718,223
Total	675,557	1,132,613
Gross Unrealized Losses
Less Than 12 Months	(3,349)	(2,051)
12 Months or More	(4,743)	(11,917)
Total	(8,092)	(13,968)
U.S. Treasury securities
Fair Value
Less Than 12 Months	10,332	170,260
12 Months or More	20,479	163,800
Total	30,811	334,060
Gross Unrealized Losses
Less Than 12 Months	(1)	(266)
12 Months or More	(7)	(1,371)
Total	(8)	(1,637)
U.S. government agency and U.S. government sponsored enterprise debt securities
Fair Value
Less Than 12 Months	180,594	69,438
12 Months or More	0	124,104
Total	180,594	193,542
Gross Unrealized Losses
Less Than 12 Months	(1,619)	(504)
12 Months or More	0	(889)
Total	(1,619)	(1,393)
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Fair Value
Less Than 12 Months	13,279	45,405
12 Months or More	21,500	16,169
Total	34,779	61,574
Gross Unrealized Losses
Less Than 12 Months	(63)	(257)
12 Months or More	(342)	(336)
Total	(405)	(593)
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Fair Value
Less Than 12 Months	122,716	81,927
12 Months or More	69,189	241,047
Total	191,905	322,974
Gross Unrealized Losses
Less Than 12 Months	(520)	(270)
12 Months or More	(1,295)	(3,808)
Total	$ (1,815)	$ (4,078)
Percentage of the total available-for-sale investment securities portfolio	26.00%	30.00%
Municipal securities
Fair Value
Less Than 12 Months	$ 47,613	$ 6,391
12 Months or More	14,536	61,107
Total	62,149	67,498
Gross Unrealized Losses
Less Than 12 Months	(1,028)	(26)
12 Months or More	(583)	(1,136)
Total	$ (1,611)	$ (1,162)
Percentage of the total available-for-sale investment securities portfolio	24.00%	12.00%
Other residential mortgage-backed securities | Investment grade
Fair Value
Less Than 12 Months	$ 7,289	$ 0
12 Months or More	6,576	7,217
Total	13,865	7,217
Gross Unrealized Losses
Less Than 12 Months	(25)	0
12 Months or More	(91)	(135)
Total	(116)	(135)
Corporate debt securities | Investment grade
Fair Value
Less Than 12 Months	45,013	25,084
12 Months or More	90,114	90,098
Total	135,127	115,182
Gross Unrealized Losses
Less Than 12 Months	(87)	(12)
12 Months or More	(1,025)	(1,042)
Total	(1,112)	(1,054)
Corporate debt securities | Non-investment grade
Fair Value
Less Than 12 Months	0	0
12 Months or More	10,524	14,681
Total	10,524	14,681
Gross Unrealized Losses
Less Than 12 Months	0	0
12 Months or More	(1,001)	(3,200)
Total	$ (1,001)	$ (3,200)
Percentage of the total available-for-sale investment securities portfolio	5.00%	5.00%
Other securities
Fair Value
Less Than 12 Months	$ 7,202	$ 15,885
12 Months or More	8,601	0
Total	15,803	15,885
Gross Unrealized Losses
Less Than 12 Months	(6)	(716)
12 Months or More	(399)	0
Total	$ (405)	$ (716)