Commitments and Contingencies (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Commitments and Contingencies
Maximum expiration period of commitments	1 year
Standby letters of credit outstanding	$ 35,900,000
Amounts drawn	0
George Mason | Exposure to repurchase loans previously sold to investors
Commitments and Contingencies
Reserve for estimated exposure to repurchase loans previously sold to investors	150,000	150,000
Floating rates
Commitments and Contingencies
Commitments to extend credit	1,300,000,000
Mortgage loan funding | George Mason
Commitments and Contingencies
Commitments to extend credit	$ 449,900,000