Loans and Allowance for Loan Losses (Summary Classification of Held to Maturity Loan Portfolio) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Held to maturity loans	$ 9,073,123	$ 9,410,982
Business [Member] | Commercial [Member]
Held to maturity loans	2,769,255	2,957,043
Real Estate - Construction and Land [Member] | Commercial [Member]
Held to maturity loans	397,598	460,853
Real Estate - Business [Member] | Commercial [Member]
Held to maturity loans	2,138,813	2,065,837
Real Estate - Personal [Member] | Personal Banking [Member]
Held to maturity loans	1,428,492	1,440,386
Consumer [Member] | Personal Banking [Member]
Held to maturity loans	1,105,785	1,164,327
Revolving Home Equity [Member] | Personal Banking [Member]
Held to maturity loans	466,946	477,518
Consumer Credit Card [Member] | Personal Banking [Member]
Held to maturity loans	752,458	831,035
Overdrafts [Member] | Personal Banking [Member]
Held to maturity loans	$ 13,776	$ 13,983