INVESTMENT SECURITIES (Details 4) (USD $)											3 Months Ended
	Mar. 31, 2012 Security	Dec. 31, 2011	Mar. 31, 2012 US Government Agencies and Government Sponsored Enterprise Debt Securities Security	Mar. 31, 2012 Residential mortgage-backed securities Security	Mar. 31, 2012 Corporate debt securities Investment grade Security	Dec. 31, 2011 Corporate debt securities Investment grade	Mar. 31, 2012 Corporate debt securities Non-investment grade Security		Dec. 31, 2011 Corporate debt securities Non-investment grade		Mar. 31, 2012 Trust Preferred Securities Security
Schedule of Available-for-sale Securities
Fair value of available for sale securities	$ 2,706,720,000	$ 3,072,578,000			$ 1,090,609,000	$ 1,322,561,000	$ 13,922,000	[1]	$ 19,615,000	[1]
Continuous unrealized loss position 12 months or more, fair value	366,815,000	359,776,000			357,426,000	350,181,000	9,389,000		9,595,000		9,400,000
Total investment securities available-for-sale portfolio (as a percent)					40.00%						1.00%
Number of securities in a continuous unrealized loss position for more than twelve months	23				18						5
Number of individual securities with a continuous unrealized loss position less than 12 months	61		6	6	47		2
Percentage of total amortized cost basis of these securities							53.00%
Gross Unrealized Losses	(79,232,000)	(107,746,000)			(67,631,000)	(95,610,000)	(10,707,000)	[1]	(11,078,000)	[1]
Gross unrealized losses in loss position twelve months or more	48,251,000	44,188,000			37,574,000	33,675,000	10,677,000		10,513,000
Gross unrealized losses, trust preferred securities, portion representing impairment loss on securities not other-than-temporarily-impaired							5,600,000
Gross unrealized losses, trust preferred securities, portion representing non-credit impairment loss on securities other-than-temporarily-impaired							5,100,000
Impairment loss relating to additional increases to the amount related to the credit loss for which an other-than-temporary impairment was previously recognized											99,000
Scheduled maturities of investment securities available-for sale, amortized cost basis
Due within one year	625,794,000
Due after one year through five years	252,183,000
Due after five years through ten years	880,483,000
Due after ten years	979,227,000
Total investment securities available-for-sale	2,737,687,000
Scheduled maturities of investment securities available-for sale, fair value
Due within one year	621,332,000
Due after one year through five years	248,610,000
Due after five years through ten years	829,519,000
Due after ten years	1,007,259,000
Total investment securities available-for-sale	$ 2,706,720,000

[1] For the three months ended March 31, 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.