Accumulated Other Comprehensive Income (Loss) - Schedule of Changes in Accumulated Other Comprehensive Income (Loss) by Component Net of Tax (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized holding gain (loss) on available-for-sale securities arising during the period, Pretax	$ (831)	$ (202)	$ (2,790)	$ 955
Beginning balance, After-tax			986
Other comprehensive (loss) income	(648)	(146)	(2,169)	792
Ending Balance, After-tax	(1,183)		(1,183)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, Pretax	(677)	1,279	1,249	92
Unrealized holding gain (loss) on available-for-sale securities arising during the period, Pretax	(831)	(202)	(2,790)	955
Amortization of held-to-maturity discount resulting from transfer, Pretax	11	17	44	47
Total other comprehensive income (loss), Pretax	(820)	(185)	(2,746)	1,002
Ending balance, Pretax	(1,497)	1,094	(1,497)	1,094
Beginning balance, Tax Effect	142	(269)	(263)	(20)
Unrealized holding gain (loss) on available-for-sale securities arising during the period, Tax Effect	175	43	586	(200)
Amortization of held-to-maturity discount resulting from transfer, Tax Effect	(3)	(4)	(9)	(10)
Total other comprehensive income (loss), Tax Effect	172	39	577	(210)
Ending Balance, Tax Effect	314	(230)	314	(230)
Beginning balance, After-tax	(535)	1,010	986	72
Unrealized holding gain (loss) on available-for-sale securities arising during the period, After-Tax	(656)	(159)	(2,204)	755
Amortization of held-to-maturity discount resulting from transfer, After-tax	8	13	35	37
Other comprehensive (loss) income	(648)	(146)	(2,169)	792
Ending Balance, After-tax	$ (1,183)	$ 864	$ (1,183)	$ 864