Commitments and Contingencies Outstanding Commitments to Extend Credit and Letters of Credit (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
ResidentialMortgagePrincipalBalanceRepurchaseRequestReceived	$ 3,600,000	$ 4,500,000
ResidentialMortgagePrincipalBalanceFHLBCreditEnhancement	212,000,000
ResidentialMortgageRepurchaseReservesFHLBCreditEnhancement	3,400,000	3,400,000
Commitments to Extend Credit [Member] | Reserve for Off-balance Sheet Activities [Member]
Valuation allowances and Reserves, Balance	4,096,386,000	4,011,741,000
Standby Letters of Credit [Member] | Reserve for Off-balance Sheet Activities [Member]
Valuation allowances and Reserves, Balance	418,963,000	425,095,000
Commercial Letters of Credit [Member] | Reserve for Off-balance Sheet Activities [Member]
Valuation allowances and Reserves, Balance	33,585,000	26,191,000
Residential Mortgage [Member] | Reserve for Off-balance Sheet Activities [Member]
Valuation allowances and Reserves, Balance	$ 5,800,000	$ 6,000,000