Loans Held for Investment and Allowance for Loan Losses - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual, past due 90 days or more and still accruing, restructured loans and foreclosed assets	$ 29,249,000	$ 25,517,000	$ 29,249,000	$ 25,517,000	$ 24,325,000
Additional funds advanced in connection with impaired loans	0		0
Loans held by subsidiaries subject to blanket liens	4,717,880,000		4,717,880,000
Available line of credit	2,516,497,000		2,516,497,000
Line of credit	0		0
Reserve for unfunded commitments (Other liabilities)	9,449,000	8,718,000	9,449,000	8,718,000	12,323,000
Total Loans	6,777,570,000	5,878,582,000	6,777,570,000	5,878,582,000	$ 6,441,868,000
Provision for Loan and Lease Losses	6,522,000	4,103,000	11,229,000	7,850,000
Federal Home Loan Bank Borrowings [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Line of credit	0		0
Unfunded Loan Commitment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for Loan and Lease Losses	949,000	1,247,000	2,875,000	2,282,000
Reversal of Provision for credit losses	$ 5,573,000	$ 5,350,000	$ 8,354,000	$ 10,132,000