Commitments and Contingencies (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended							9 Months Ended
	Feb. 28, 2011 Directors	Sep. 30, 2012 Commitments to Extend Credit	Dec. 31, 2011 Commitments to Extend Credit	Sep. 30, 2011 Commitments to Extend Credit	Sep. 30, 2012 Standby Letters of Credit	Dec. 31, 2011 Standby Letters of Credit	Sep. 30, 2011 Standby Letters of Credit	Sep. 30, 2012 Recourse Obligation on Mortgage Loans Sold	Dec. 31, 2011 Recourse Obligation on Mortgage Loans Sold	Sep. 30, 2011 Recourse Obligation on Mortgage Loans Sold	Sep. 30, 2012 Obligation to Repurchase Receivables Sold	Sep. 30, 2012 Obligation to Repurchase Receivables Sold Recourse Obligation on Mortgage Loans Sold
Guarantor Obligations [Line Items]
Unused commitments		$ 5,677,233	$ 5,636,942	$ 5,890,227
Guarantor obligations amount					62,214	57,446	57,933	195,515	207,963	216,950		108,110
Reserve for estimated losses arising from repurchase of loans											$ 3,250
General maximum recourse period, days								120 days
Number of directors in complaint	5