Loans Held for Investment and Allowance for Loan Losses - Non-Accrual Loans, Loans Still Accruing and Past Due 90 Days or More and Restructured Loans (Parenthetical) (Detail) - USD ($)		Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021
Loans and Leases Receivable Disclosure [Line Items]
Troubled debt restructured loans still accruing	[1]	$ 19,000	$ 21,000	$ 22,000
Doubtful [Member]
Loans and Leases Receivable Disclosure [Line Items]
Troubled debt restructured loans still accruing		$ 1,951,000	$ 6,721,000	$ 4,732,000

[1] Troubled debt restructured loans of $1,951,000, $4,732,000 and $6,721,000, for which interest collection is doubtful are included in nonaccrual loans as of September 30, 2022 and 2021, and December 31, 2021, respectively.