INVESTMENT SECURITIES (Details 4) (USD $) In Thousands, unless otherwise specified	Sep. 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	$ 1,787,931	$ 620,165
Continuous unrealized loss position less than 12 months, unrealized losses	(47,386)	(6,989)
Continuous unrealized loss position 12 months or more, fair value	125,997	195,271
Continuous unrealized loss position 12 months or more, unrealized losses	(10,254)	(19,739)
Continuous unrealized loss position total, fair value	1,913,928	815,436
Continuous unrealized loss position total, unrealized losses	(57,640)	(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	310,061	95,232
Continuous unrealized loss position less than 12 months, unrealized losses	(2,560)	(71)
Continuous unrealized loss position total, fair value	310,061	95,232
Continuous unrealized loss position total, unrealized losses	(2,560)	(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	275,999	24,912
Continuous unrealized loss position less than 12 months, unrealized losses	(8,651)	(82)
Continuous unrealized loss position total, fair value	275,999	24,912
Continuous unrealized loss position total, unrealized losses	(8,651)	(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	136,408	10,013
Continuous unrealized loss position less than 12 months, unrealized losses	(3,516)	(36)
Continuous unrealized loss position total, fair value	136,408	10,013
Continuous unrealized loss position total, unrealized losses	(3,516)	(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	572,399	215,826
Continuous unrealized loss position less than 12 months, unrealized losses	(12,767)	(678)
Continuous unrealized loss position 12 months or more, fair value	25,511
Continuous unrealized loss position 12 months or more, unrealized losses	(683)
Continuous unrealized loss position total, fair value	597,910	215,826
Continuous unrealized loss position total, unrealized losses	(13,450)	(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	180,857	48,363
Continuous unrealized loss position less than 12 months, unrealized losses	(16,410)	(731)
Continuous unrealized loss position total, fair value	180,857	48,363
Continuous unrealized loss position total, unrealized losses	(16,410)	(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	14,692
Continuous unrealized loss position less than 12 months, unrealized losses	(797)
Continuous unrealized loss position total, fair value	14,692
Continuous unrealized loss position total, unrealized losses	(797)
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	287,598	225,819
Continuous unrealized loss position less than 12 months, unrealized losses	(2,594)	(5,391)
Continuous unrealized loss position 12 months or more, fair value	86,201	182,697
Continuous unrealized loss position 12 months or more, unrealized losses	(3,798)	(12,181)
Continuous unrealized loss position total, fair value	373,799	408,516
Continuous unrealized loss position total, unrealized losses	(6,392)	(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	14,285	12,574
Continuous unrealized loss position 12 months or more, unrealized losses	(5,773)	(7,558)
Continuous unrealized loss position total, fair value	14,285	12,574
Continuous unrealized loss position total, unrealized losses	(5,773)	(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	9,917
Continuous unrealized loss position less than 12 months, unrealized losses	(91)
Continuous unrealized loss position total, fair value	9,917
Continuous unrealized loss position total, unrealized losses	$ (91)