Qualified Affordable Housing Project Investments - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Investments In Affordable Housing Projects [Abstract]
Investment for qualified affordable housing projects included in other assets	$ 13,303,000		$ 13,303,000		$ 11,911,000
Unfunded commitments related to the investments in qualified affordable housing projects	6,629,000		6,629,000		$ 5,944,000
Recognized amortization expense	203,000	$ 156,000	608,000	$ 489,000
Recognized tax credits and other benefits from its investment in affordable housing tax credits	339,000	304,000	1,015,000	888,000
Impairment losses related to its investments in qualified affordable housing projects	$ 0	$ 0	$ 0	$ 0