Accumulated Other Comprehensive Income (Loss) - Schedule of Changes in Accumulated Other Comprehensive (Loss) Income by Component Net of Tax (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized holding gain (loss) on available-for-sale securities arising during the period, Pretax	$ (202)	$ 275	$ 955	$ 1,786
Beginning balance, After-tax			72
Other comprehensive income (loss)	(146)	229	792	1,447
Ending Balance, After-tax	864		864
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, Pretax	1,279	(245)	92	(1,786)
Unrealized holding gain (loss) on available-for-sale securities arising during the period, Pretax	(202)	275	955	1,786
Amortization of held-to-maturity discount resulting from transfer, Pretax	17	15	47	45
Total other comprehensive income (loss), Pretax	(185)	290	1,002	1,831
Ending balance, Pretax	1,094	45	1,094	45
Beginning balance, Tax Effect	(269)	51	(20)	374
Unrealized holding gain (loss) on available-for-sale securities arising during the period, Tax Effect	43	(58)	(200)	(374)
Amortization of held-to-maturity discount resulting from transfer, Tax Effect	(4)	(3)	(10)	(10)
Total other comprehensive income (loss), Tax Effect	39	(61)	(210)	(384)
Ending Balance, Tax Effect	(230)	(10)	(230)	(10)
Beginning balance, After-tax	1,010	(194)	72	(1,412)
Unrealized holding gain (loss) on available-for-sale securities arising during the period, After-Tax	(159)	217	755	1,412
Amortization of held-to-maturity discount resulting from transfer, After-tax	13	12	37	35
Other comprehensive income (loss)	(146)	229	792	1,447
Ending Balance, After-tax	$ 864	$ 35	$ 864	$ 35