Commitments and Contingencies (Details) (USD $)	3 Months Ended	12 Months Ended
	Jun. 30, 2010	Dec. 31, 2012 item	Dec. 31, 2011	Dec. 31, 2010
Commitments and Contingencies
Rent expense under operating leases		$ 11,100,000	$ 9,700,000	$ 8,700,000
Minimum sublease rentals due in the future		7,700,000
Repurchase of loan as a result of recourse provisions, number		1
Repurchase of loan as a result of recourse provisions, amount		190,000
Principal balance of loans sold with recourse provisions		342,200,000	305,900,000
Outstanding option balance			5,800,000
Available-for-sale, amortized cost		330,481,000	327,137,000
Available-for-sale, estimated fair value		336,300,000	344,187,000
Outstanding standby letters of credit		213,000	265,000
Alleged tax deficiency including interest and penalties related to 2006 through 2008 tax years		13,300,000
Proceeds from litigation settlement	6,200,000
Litigation settlement payment	7,900,000
Maximum
Commitments and Contingencies
Standby letters of credit, term extended by guarantee		1 year
Collateralized Securities | GSE pass-through certificates
Commitments and Contingencies
Available-for-sale, amortized cost		7,800,000
Available-for-sale, estimated fair value		$ 8,200,000