INVESTMENT SECURITIES (Details) (USD $)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	$ 3,132,968,000		$ 2,900,410,000
Gross Unrealized Gains	47,356,000		24,383,000
Gross Unrealized Losses	(107,746,000)		(48,852,000)
Fair Value	3,072,578,000		2,875,941,000
Other than temporary impairment, pre-tax basis, credit portion recognized in earnings	633,000		16,700,000
Other than temporary impairment, pre-tax basis, non-credit portion recognized in other comprehensive income	5,100,000		15,400,000
U.S. Treasury securities
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	19,892,000		19,847,000
Gross Unrealized Gains	833,000		607,000
Fair Value	20,725,000		20,454,000
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	575,148,000		1,349,289,000
Gross Unrealized Gains	1,709,000		2,297,000
Gross Unrealized Losses	(279,000)		(18,121,000)
Fair Value	576,578,000		1,333,465,000
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	46,008,000		18,620,000
Gross Unrealized Gains	3,307,000		512,000
Fair Value	49,315,000		19,132,000
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	963,688,000		295,140,000
Gross Unrealized Gains	30,854,000		11,574,000
Gross Unrealized Losses	(772,000)
Fair Value	993,770,000		306,714,000
Municipal securities
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	76,255,000
Gross Unrealized Gains	3,696,000
Gross Unrealized Losses	(5,000)
Fair Value	79,946,000
Other residential mortgage-backed securities: | Non-investment grade
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost			14,996,000
Gross Unrealized Losses			(8,742,000)
Fair Value			6,254,000
Corporate debt securities | Investment grade
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	1,411,409,000		1,056,537,000
Gross Unrealized Gains	6,762,000		9,095,000
Gross Unrealized Losses	(95,610,000)		(8,765,000)
Fair Value	1,322,561,000		1,056,867,000
Corporate debt securities | Non-investment grade
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	30,693,000	[1]	50,015,000	[1]
Gross Unrealized Gains			31,000	[1]
Gross Unrealized Losses	(11,078,000)	[1]	(11,316,000)	[1]
Fair Value	19,615,000	[1]	38,730,000	[1]
Other securities
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	9,875,000		95,966,000
Gross Unrealized Gains	195,000		267,000
Gross Unrealized Losses	(2,000)		(1,908,000)
Fair Value	$ 10,068,000		$ 94,325,000

[1] For 2011, the Company recorded $633 thousand, on a pre-tax basis, of OTTI through earnings and $5.1 million of the non-credit portion of OTTI for pooled trust securities and other mortgage-backed securities in other comprehensive income. For 2010, the Company recorded $16.7 million, on a pre-tax basis, of OTTI through earnings and $15.4 million of the non-credit portion of OTTI for pooled trust securities and other mortgage-backed securities in other comprehensive income.