Loans (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Partial charge-offs on impaired loans	$ 108,300,000	$ 103,800,000
Allowance for loans individually evaluated for impairment	9,500,000	15,900,000
Recorded investment, related to loans	33,700,000	52,700,000
TDRs included in nonaccrual loan totals	98,600,000	100,400,000
TDRs included in accruing loan totals	34,600,000	28,700,000
Nonaccrual TDRs considered current	52,800,000	79,900,000
Specific reserves related to troubled debt restructuring	4,400,000	9,100,000
Commitments to lend additional funds to borrowers whose terms had been modified in a TDR	5,100,000	4,000,000
Additional specific reserves related to troubled debt restructurings	252,000
Modified substandard commercial loans, total recorded investment	3,600,000
Modified substandard consumer loans, total recorded investment	6,300,000
Recorded investment	21,164,000
Financing Receivable With No Related Allowance Recorded [Member]
Financing Receivable, Recorded Investment [Line Items]
Partial charge-offs on impaired loans	91,000,000	83,700,000
Financing Receivable With A Related Allowance Recorded [Member]
Financing Receivable, Recorded Investment [Line Items]
Partial charge-offs on impaired loans	17,300,000	20,100,000
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded investment	3,201,000
Accruing [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded investment	205,000
Nonaccrual [Member]
Financing Receivable, Recorded Investment [Line Items]
Recorded investment	$ 20,000,000