INVESTMENT SECURITIES (Details) (USD $)	9 Months Ended			12 Months Ended
	Sep. 30, 2012		Sep. 30, 2011	Dec. 31, 2011
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	$ 2,240,496,000			$ 3,132,968,000
Gross Unrealized Gains	36,205,000			47,356,000
Gross Unrealized Losses	(38,853,000)			(107,746,000)
Fair Value	2,237,848,000			3,072,578,000
Other than temporary impairment, pre-tax basis, credit portion recognized in earnings	99,000		464,000	633,000
Other than temporary impairment, pre-tax basis, non-credit portion recognized in other comprehensive income	5,100,000			5,100,000
U.S. Treasury securities
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	398,666,000			19,892,000
Gross Unrealized Gains	1,368,000			833,000
Gross Unrealized Losses	(2,000)
Fair Value	400,032,000			20,725,000
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	197,384,000			575,148,000
Gross Unrealized Gains	661,000			1,709,000
Gross Unrealized Losses				(279,000)
Fair Value	198,045,000			576,578,000
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	80,225,000			46,008,000
Gross Unrealized Gains	5,601,000			3,307,000
Fair Value	85,826,000			49,315,000
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	981,123,000			963,688,000
Gross Unrealized Gains	23,105,000			30,854,000
Gross Unrealized Losses	(331,000)			(772,000)
Fair Value	1,003,897,000			993,770,000
Municipal securities
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	108,834,000			76,255,000
Gross Unrealized Gains	4,774,000			3,696,000
Gross Unrealized Losses	(11,000)			(5,000)
Fair Value	113,597,000			79,946,000
Corporate debt securities | Investment grade
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	441,908,000			1,411,409,000
Gross Unrealized Gains	315,000			6,762,000
Gross Unrealized Losses	(29,504,000)			(95,610,000)
Fair Value	412,719,000			1,322,561,000
Corporate debt securities | Non-investment grade
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	22,493,000	[1]		30,693,000	[1]
Gross Unrealized Gains	119,000	[1]
Gross Unrealized Losses	(9,002,000)	[1]		(11,078,000)	[1]
Fair Value	13,610,000	[1]		19,615,000	[1]
Other securities
Schedule of Available-for-sale Securities
Investment securities available-for-sale, amortized cost	9,863,000			9,875,000
Gross Unrealized Gains	262,000			195,000
Gross Unrealized Losses	(3,000)			(2,000)
Fair Value	$ 10,122,000			$ 10,068,000

[1] For the nine months ended September 30, 2012, the Company recorded $99 thousand, on a pre-tax basis, of the credit portion of OTTI through earnings and $5.1 million of the non-credit portion of OTTI for pooled trust preferred securities in other comprehensive income. The Company recorded $633 thousand, on a pre-tax basis, of the credit portion of OTTI through earnings and $5.1 million of the non-credit portion of OTTI for pooled trust preferred securities and other mortgage-backed securities in other comprehensive income for the year ended December 31, 2011.