INVESTMENT SECURITIES (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	$ 2,504,755		$ 2,786,490
Gross Unrealized Gains	15,232		12,203
Gross Unrealized Losses	(45,243)		(64,896)
Fair Value	2,474,744		2,733,797
U.S. Treasury securities
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	431,307		495,053
Gross Unrealized Gains	91		201
Gross Unrealized Losses	(3,145)		(3,622)
Fair Value	428,253		491,632
U.S. Government agency and U.S. Government sponsored enterprise debt securities
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	391,470		406,807
Gross Unrealized Gains	763		242
Gross Unrealized Losses	(7,548)		(12,726)
Fair Value	384,685		394,323
U.S. Government agency and U.S. Government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	120,999		182,257
Gross Unrealized Gains	769		1,062
Gross Unrealized Losses	(2,661)		(4,449)
Fair Value	119,107		178,870
U.S. Government agency and U.S. Government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	829,005		892,435
Gross Unrealized Gains	7,331		7,729
Gross Unrealized Losses	(12,231)		(14,927)
Fair Value	824,105		885,237
Municipal securities
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	290,241		297,390
Gross Unrealized Gains	3,197		1,122
Gross Unrealized Losses	(9,541)		(17,533)
Fair Value	283,897		280,979
Other residential mortgage-backed securities: | Investment grade
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	58,450		48,129
Gross Unrealized Losses	(1,443)		(1,802)
Fair Value	57,007		46,327
Other commercial mortgage-backed securities: | Investment grade
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	50,999		51,000
Gross Unrealized Gains	420		617
Fair Value	51,419		51,617
Corporate debt securities | Investment grade
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	212,593		312,726
Gross Unrealized Gains	60		613
Gross Unrealized Losses	(2,962)		(3,344)
Fair Value	209,691		309,995
Corporate debt securities | Non-investment grade
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	20,577	[1]	20,668	[1]
Gross Unrealized Gains	28		62
Gross Unrealized Losses	(5,093)	[1]	(5,629)	[1]
Fair Value	15,512	[1]	15,101	[1]
Other securities
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	99,114		80,025
Gross Unrealized Gains	2,573		555
Gross Unrealized Losses	(619)		(864)
Fair Value	$ 101,068		$ 79,716

[1] For the three months ended March 31, 2014 and the year ended December 31, 2013, the Company did not record any OTTI.