Loans and Allowance for Loan Losses (Credit Quality of Commercial Loan Portfolio) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Total	$ 5,305,666	$ 5,483,733
Business [Member] | Pass [Member]
Total	2,614,530	2,801,328
Real Estate - Construction and Land [Member] | Pass [Member]
Total	304,192	327,167
Real Estate - Business [Member] | Pass [Member]
Total	1,941,388	1,878,005
Pass [Member]
Total	4,860,110	5,006,500
Business [Member] | Special Mention [Member]
Total	54,141	67,142
Real Estate - Construction and Land [Member] | Special Mention [Member]
Total	9,949	29,345
Real Estate - Business [Member] | Special Mention [Member]
Total	69,918	77,527
Special Mention [Member]
Total	134,008	174,014
Business [Member] | Substandard [Member]
Total	74,250	79,640
Real Estate - Construction and Land [Member] | Substandard [Member]
Total	57,150	51,589
Real Estate - Business [Member] | Substandard [Member]
Total	111,559	94,063
Substandard [Member]
Total	242,959	225,292
Business [Member] | Non-accrual [Member]
Total	26,334	8,933
Real Estate - Construction and Land [Member] | Non-accrual [Member]
Total	26,307	52,752
Real Estate - Business [Member] | Non-accrual [Member]
Total	15,948	16,242
Non-accrual [Member]
Total	68,589	77,927
Business [Member]
Total	2,769,255	2,957,043
Real Estate - Construction and Land [Member]
Total	397,598	460,853
Real Estate - Business [Member]
Total	$ 2,138,813	$ 2,065,837