Commitments and Contingent Liabilities - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Loan commitments outstanding	$ 5,302,560	$ 3,610,777
Loan commitments expiry period	1 year
George Mason [Member]
Loss Contingencies [Line Items]
Reserve for possible losses due to the repurchase of loans previously sold to investors	$ 1,330
Commitments to Extend Credit [Member] | George Mason [Member] | Short-term Contract with Customer [Member]
Loss Contingencies [Line Items]
Additional commitments to extend credit	498,512
Commercial Letters of Credit [Member]
Loss Contingencies [Line Items]
Letters of credit issued	5,092	5,092
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Letters of credit issued	$ 147,940	$ 145,105