INVESTMENT SECURITIES (Details 4) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Continuous unrealized loss position, fair values of investment securities available-for-sale
Continuous unrealized loss position less than 12 months, fair value	$ 1,577,597	$ 620,165
Continuous unrealized loss position less than 12 months, unrealized losses	(40,605)	(6,989)
Continuous unrealized loss position 12 months or more, fair value	152,581	195,271
Continuous unrealized loss position 12 months or more, unrealized losses	(11,679)	(19,739)
Continuous unrealized loss position total, fair value	1,730,178	815,436
Continuous unrealized loss position total, unrealized losses	(52,284)	(26,728)
U.S. Treasury securities
Continuous unrealized loss position, fair values of investment securities available-for-sale
Continuous unrealized loss position less than 12 months, fair value	403,759	95,232
Continuous unrealized loss position less than 12 months, unrealized losses	(3,963)	(71)
Continuous unrealized loss position total, fair value	403,759	95,232
Continuous unrealized loss position total, unrealized losses	(3,963)	(71)
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	243,025	24,912
Continuous unrealized loss position less than 12 months, unrealized losses	(6,990)	(82)
Continuous unrealized loss position total, fair value	243,025	24,912
Continuous unrealized loss position total, unrealized losses	(6,990)	(82)
U.S. Government agency and U.S. Government sponsored enterprise mortgage-backed securities - Commercial 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	112,519	10,013
Continuous unrealized loss position less than 12 months, unrealized losses	(3,145)	(36)
Continuous unrealized loss position total, fair value	112,519	10,013
Continuous unrealized loss position total, unrealized losses	(3,145)	(36)
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	508,853	215,826
Continuous unrealized loss position less than 12 months, unrealized losses	(10,991)	(678)
Continuous unrealized loss position 12 months or more, fair value	13,909
Continuous unrealized loss position 12 months or more, unrealized losses	(289)
Continuous unrealized loss position total, fair value	522,762	215,826
Continuous unrealized loss position total, unrealized losses	(11,280)	(678)
Municipal securities
Continuous unrealized loss position, fair values of investment securities available-for-sale
Continuous unrealized loss position less than 12 months, fair value	181,003	48,363
Continuous unrealized loss position less than 12 months, unrealized losses	(14,424)	(731)
Continuous unrealized loss position total, fair value	181,003	48,363
Continuous unrealized loss position total, unrealized losses	(14,424)	(731)
Other residential mortgage-backed 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	15,203
Continuous unrealized loss position less than 12 months, unrealized losses	(778)
Continuous unrealized loss position total, fair value	15,203
Continuous unrealized loss position total, unrealized losses	(778)
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	105,966	225,819
Continuous unrealized loss position less than 12 months, unrealized losses	(282)	(5,391)
Continuous unrealized loss position 12 months or more, fair value	125,053	182,697
Continuous unrealized loss position 12 months or more, unrealized losses	(4,947)	(12,181)
Continuous unrealized loss position total, fair value	231,019	408,516
Continuous unrealized loss position total, unrealized losses	(5,229)	(17,572)
Corporate debt securities | Non-investment grade
Continuous unrealized loss position, fair values of investment securities available-for-sale
Continuous unrealized loss position 12 months or more, fair value	13,619	12,574
Continuous unrealized loss position 12 months or more, unrealized losses	(6,443)	(7,558)
Continuous unrealized loss position total, fair value	13,619	12,574
Continuous unrealized loss position total, unrealized losses	(6,443)	(7,558)
Other securities
Continuous unrealized loss position, fair values of investment securities available-for-sale
Continuous unrealized loss position less than 12 months, fair value	7,269
Continuous unrealized loss position less than 12 months, unrealized losses	(32)
Continuous unrealized loss position total, fair value	7,269
Continuous unrealized loss position total, unrealized losses	$ (32)