INVESTMENT SECURITIES (Details 3) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Continuous unrealized loss position, fair values of investment securities available-for-sale
Continuous unrealized loss position less than 12 months, fair value	$ 687,562	$ 1,108,347
Continuous unrealized loss position less than 12 months, unrealized losses	(30,981)	(63,558)
Continuous unrealized loss position 12 months or more, fair value	366,815	359,776
Continuous unrealized loss position 12 months or more, unrealized losses	(48,251)	(44,188)
Continuous unrealized loss position total, fair value	1,054,377	1,468,123
Continuous unrealized loss position total, unrealized losses	(79,232)	(107,746)
U.S. Government agency and U.S. Government sponsored enterprise debt securities
Continuous unrealized loss position, fair values of investment securities available-for-sale
Continuous unrealized loss position less than 12 months, fair value	141,223	143,265
Continuous unrealized loss position less than 12 months, unrealized losses	(525)	(279)
Continuous unrealized loss position total, fair value	141,223	143,265
Continuous unrealized loss position total, unrealized losses	(525)	(279)
U.S. Government agency and U.S. Government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Continuous unrealized loss position, fair values of investment securities available-for-sale
Continuous unrealized loss position less than 12 months, fair value	93,968	195,393
Continuous unrealized loss position less than 12 months, unrealized losses	(369)	(772)
Continuous unrealized loss position total, fair value	93,968	195,393
Continuous unrealized loss position total, unrealized losses	(369)	(772)
Municipal securities
Continuous unrealized loss position, fair values of investment securities available-for-sale
Continuous unrealized loss position less than 12 months, fair value		1,158
Continuous unrealized loss position less than 12 months, unrealized losses		(5)
Continuous unrealized loss position total, fair value		1,158
Continuous unrealized loss position total, unrealized losses		(5)
Corporate debt securities | Investment grade
Continuous unrealized loss position, fair values of investment securities available-for-sale
Continuous unrealized loss position less than 12 months, fair value	450,019	754,055
Continuous unrealized loss position less than 12 months, unrealized losses	(30,057)	(61,935)
Continuous unrealized loss position 12 months or more, fair value	357,426	350,181
Continuous unrealized loss position 12 months or more, unrealized losses	(37,574)	(33,675)
Continuous unrealized loss position total, fair value	807,445	1,104,236
Continuous unrealized loss position total, unrealized losses	(67,631)	(95,610)
Corporate debt securities | Non-investment grade
Continuous unrealized loss position, fair values of investment securities available-for-sale
Continuous unrealized loss position less than 12 months, fair value	2,352	9,973
Continuous unrealized loss position less than 12 months, unrealized losses	(30)	(565)
Continuous unrealized loss position 12 months or more, fair value	9,389	9,595
Continuous unrealized loss position 12 months or more, unrealized losses	(10,677)	(10,513)
Continuous unrealized loss position total, fair value	11,741	19,568
Continuous unrealized loss position total, unrealized losses	(10,707)	(11,078)
Other securities
Continuous unrealized loss position, fair values of investment securities available-for-sale
Continuous unrealized loss position less than 12 months, fair value		4,503
Continuous unrealized loss position less than 12 months, unrealized losses		(2)
Continuous unrealized loss position total, fair value		4,503
Continuous unrealized loss position total, unrealized losses		$ (2)