Loans Held for Investment and Allowance for Loan Losses - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 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	$ 39,698,000	$ 24,619,000	$ 39,698,000	$ 24,619,000	$ 24,325,000
Additional funds advanced in connection with impaired loans	0		0
Loans held by subsidiaries subject to blanket liens	2,600,103,000		2,600,103,000
Available line of credit	2,538,345,000		2,538,345,000
line of Credit	0		0
Undisbursed commitments	45,000,000		45,000,000
Reserve for unfunded commitments (Other liabilities)	7,903,000	10,879,000	7,903,000	10,879,000	12,323,000
Total Loans	6,994,696,000	6,255,488,000	6,994,696,000	6,255,488,000	$ 6,441,868,000
Provision for Loan and Lease Losses	3,821,000	1,060,000	15,050,000	8,910,000
Unfunded Loan Commitment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for Loan and Lease Losses	1,545,000	2,161,000	4,419,000	4,443,000
Reversal of Provision for credit losses	$ 2,276,000	$ 3,221,000	$ 10,631,000	$ 13,353,000