INVESTMENT SECURITIES (Details 4) (USD $)	12 Months Ended								12 Months Ended											12 Months Ended
	Dec. 31, 2011 Security	Dec. 31, 2010 Security	Dec. 31, 2009	Dec. 31, 2008 ASC 320-10-65 Other-Than-Temporary Impairments	Dec. 31, 2011 US Government Agencies and Government Sponsored Enterprise Debt Securities Security	Dec. 31, 2010 US Government Agencies and Government Sponsored Enterprise Debt Securities Security	Dec. 31, 2011 Residential mortgage-backed securities Security	Dec. 31, 2010 Residential mortgage-backed securities Non-investment grade	Dec. 31, 2011 Mortgage-backed securities Security	Dec. 31, 2010 Mortgage-backed securities Security	Dec. 31, 2011 Corporate debt securities Investment grade Security	Dec. 31, 2010 Corporate debt securities Investment grade Security	Dec. 31, 2011 Corporate debt securities Non-investment grade Security		Dec. 31, 2010 Corporate debt securities Non-investment grade Security		Dec. 31, 2011 Municipal security Security	Dec. 31, 2011 Other securities Security	Dec. 31, 2010 Other securities Security	Dec. 31, 2011 Trust Preferred Securities Security	Dec. 31, 2010 Trust Preferred Securities Security	Dec. 31, 2009 Trust Preferred Securities Security
Schedule of Available-for-sale Securities
Fair value of available for sale securities	$ 3,072,578,000	$ 2,875,941,000						$ 6,254,000			$ 1,322,561,000	$ 1,056,867,000	$ 19,615,000	[1]	$ 38,730,000	[1]	$ 79,946,000	$ 10,068,000	$ 94,325,000
Continuous unrealized loss position 12 months or more, fair value	359,776,000	16,180,000						6,254,000		6,300,000	350,181,000		9,595,000		9,926,000					9,600,000	9,900,000
Total investment securities available-for-sale portfolio (as a percent)											43.00%									1.00%
Number of securities in a continuous unrealized loss position for more than twelve months	24	6								1	19									5	5
Number of securities for which noncredit-related impairment losses have been recorded during the period																					5	14
Cumulative impact, before taxes, of implementation of new accounting principle on retained earnings				14,000,000
Cumulative impact, net of taxes, of implementation of new accounting principle on retained earnings				8,100,000
Number of individual securities with a continuous unrealized loss position less than 12 months	116	129			5	33	16				89	46	4		8		1	1	42
Percentage of total amortized cost basis of these securities													52.00%
Gross Unrealized Losses	(107,746,000)	(48,852,000)						(8,742,000)		(8,700,000)	(95,610,000)	(8,765,000)	(11,078,000)	[1]	(11,316,000)	[1]	(5,000)	(2,000)	(1,908,000)
Gross unrealized losses in loss position twelve months or more	44,188,000	19,435,000						8,742,000			33,675,000		10,513,000		10,693,000
Gross unrealized losses, trust preferred securities, portion representing impairment loss on securities not other-than-temporarily-impaired													5,400,000
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																				633,000
Noncredit-related impairment losses																					6,700,000	14,100,000
Number of private-label available-for-sale mortgage-backed securities sold									1
Net impairment loss on investment securities available-for-sale recognized in earnings	633,000	16,669,000	107,671,000						6,300,000
Scheduled maturities of investment securities available-for sale, amortized cost basis
Due within one year	708,317,000
Due after one year through five years	372,837,000
Due after five years through ten years	1,001,425,000
Due after ten years	1,050,389,000
Total investment securities available-for-sale	3,132,968,000
Scheduled maturities of investment securities available-for sale, fair value
Due within one year	704,059,000
Due after one year through five years	357,446,000
Due after five years through ten years	933,429,000
Due after ten years	1,077,644,000
Total investment securities available-for-sale	3,072,578,000
Proceeds from sales of available-for-sale securities	702,616,000	1,338,910,000	1,650,680,000
Realized gains on sale of securities	9,703,000	31,237,000	11,923,000
Tax expense on the sale of investment securities	4,100,000	13,100,000	5,000,000
Par value of securities pledged to secure public deposits	2,170,000,000	1,880,000,000
Held-to-maturity securities transferred to available for sale securities			$ 681,400,000

[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.