Commitments and Contingent Liabilities - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Loss Contingencies [Line Items]
Loan commitments outstanding	$ 7,397,308	$ 6,847,550
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	$ 1,081	1,150
Commitments to Extend Credit [Member] | George Mason [Member] | Short-term Contract with Customer [Member]
Loss Contingencies [Line Items]
Additional commitments to extend credit	714,635	571,792
Commercial Letters of Credit [Member]
Loss Contingencies [Line Items]
Letters of credit issued	17,408	14,774
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Letters of credit issued	$ 156,599	$ 164,743