Business Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Business segment financial information
Net Interest Income	$ 97,499	$ 103,928	$ 197,196	$ 211,581
Provision for Credit Losses	3,600	15,939	8,291	36,650
Net Interest Income After Provision for Credit Losses	93,899	87,989	188,905	174,931
Noninterest Income	49,463	68,874	103,385	140,656
Noninterest Expense	(93,774)	(85,918)	(179,856)	(167,624)
Income Before Provision for Income Taxes	49,588	70,945	112,434	147,963
Provision for Income Taxes	(14,440)	(24,381)	(34,926)	(48,663)
Net Income	35,148	46,564	77,508	99,300
Total Assets	13,161,204	12,855,845	13,161,204	12,855,845	13,126,787
Retail Banking
Business segment financial information
Number of branch locations through which products and services are delivered to customers	71
Number of ATM's through which products and services are delivered to customers	508
Net Interest Income	43,890	48,246	88,314	97,551
Provision for Credit Losses	5,585	9,871	10,628	25,227
Net Interest Income After Provision for Credit Losses	38,305	38,375	77,686	72,324
Noninterest Income	21,697	25,806	41,817	49,273
Noninterest Expense	(52,345)	(43,436)	(96,244)	(85,769)
Income Before Provision for Income Taxes	7,657	20,745	23,259	35,828
Provision for Income Taxes	(2,833)	(7,676)	(8,606)	(13,256)
Net Income	4,824	13,069	14,653	22,572
Total Assets	3,058,041	3,156,403	3,058,041	3,156,403
Commercial Banking
Business segment financial information
Number of branches in which international banking and operations is included	11
Net Interest Income	34,686	36,319	69,689	77,446
Provision for Credit Losses	397	6,206	209	11,347
Net Interest Income After Provision for Credit Losses	34,289	30,113	69,480	66,099
Noninterest Income	9,741	11,697	18,798	21,715
Noninterest Expense	(24,159)	(24,977)	(48,581)	(48,839)
Income Before Provision for Income Taxes	19,871	16,833	39,697	38,975
Provision for Income Taxes	(6,974)	(6,322)	(13,806)	(14,321)
Net Income	12,897	10,511	25,891	24,654
Total Assets	2,266,089	2,326,589	2,266,089	2,326,589
Investment Services
Business segment financial information
Net Interest Income	3,792	4,215	7,655	8,538
Provision for Credit Losses		(127)	(140)	88
Net Interest Income After Provision for Credit Losses	3,792	4,342	7,795	8,450
Noninterest Income	15,234	14,310	30,284	29,337
Noninterest Expense	(15,043)	(15,553)	(30,447)	(29,598)
Income Before Provision for Income Taxes	3,983	3,099	7,632	8,189
Provision for Income Taxes	(1,474)	(1,147)	(2,824)	(3,031)
Net Income	2,509	1,952	4,808	5,158
Total Assets	221,347	312,676	221,347	312,676
Treasury and Other
Business segment financial information
Net Interest Income	15,131	15,148	31,538	28,046
Provision for Credit Losses	(2,382)	(11)	(2,406)	(12)
Net Interest Income After Provision for Credit Losses	17,513	15,159	33,944	28,058
Noninterest Income	2,791	17,061	12,486	40,331
Noninterest Expense	(2,227)	(1,952)	(4,584)	(3,418)
Income Before Provision for Income Taxes	18,077	30,268	41,846	64,971
Provision for Income Taxes	(3,159)	(9,236)	(9,690)	(18,055)
Net Income	14,918	21,032	32,156	46,916
Total Assets	$ 7,615,727	$ 7,060,177	$ 7,615,727	$ 7,060,177