Loans and Allowance for Loan Losses (Summary Classification of Held to Maturity Loan Portfolio) (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Held to maturity loans	$ 9,237,078	$ 9,410,982
Business [Member] | Commercial [Member]
Held to maturity loans	2,921,556	2,957,043
Real Estate - Construction and Land [Member] | Commercial [Member]
Held to maturity loans	433,464	460,853
Real Estate - Business [Member] | Commercial [Member]
Held to maturity loans	2,097,691	2,065,837
Real Estate - Personal [Member] | Personal Banking [Member]
Held to maturity loans	1,438,030	1,440,386
Consumer [Member] | Personal Banking [Member]
Held to maturity loans	1,108,909	1,164,327
Revolving Home Equity [Member] | Personal Banking [Member]
Held to maturity loans	467,391	477,518
Consumer Credit Card [Member] | Personal Banking [Member]
Held to maturity loans	764,844	831,035
Overdrafts [Member] | Personal Banking [Member]
Held to maturity loans	$ 5,193	$ 13,983