Loans And Allowance For Credit Losses - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounts Notes And Loans Receivable [Line Items]
Loans held by subsidiaries subject to blanket liens	$ 3,526,667,000
Nonaccrual, past due 90 days or more and still accruing, restructured loans and foreclosed assets	34,158,000	$ 42,898,000
Nonaccrual loans	31,652,000	42,619,000
Interest income recognized on impaired loans	2,122,000	1,006,000	$ 750,000
Additional funds advanced in connection with impaired loans	0
Unfunded loan commitments	6,436,000	5,486,000
Provision for loan losses	$ (2,089,000)	$ 16,048,000
Default for purposes of this disclosure is a troubled debt restructured loan	12 months	12 months
Commitments to lend additional funds to borrowers with loan that have been modified as TDRs	$ 0
Total Loans	5,388,972,000	$ 5,171,033,000
Residentials Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Total Loans	459,000,000	0
Unfunded Loan Commitment [Member]
Accounts Notes And Loans Receivable [Line Items]
Provision for loan losses	$ 950,000	$ 3,469,000