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
	Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized holding gain (loss) on available-for-sale securities arising during the period, Pretax	$ (3,607)	$ 540
Beginning balance, After-tax	986
Other comprehensive income (loss)	(2,836)	438
Ending Balance, After-tax	(1,850)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, Pretax	1,249	92
Unrealized holding gain (loss) on available-for-sale securities arising during the period, Pretax	(3,607)	540
Amortization of held-to-maturity discount resulting from transfer, Pretax	16	14
Total other comprehensive income (loss), Pretax	(3,591)	554
Ending balance, Pretax	(2,342)	646
Beginning balance, Tax Effect	(263)	(20)
Unrealized holding gain (loss) on available-for-sale securities arising during the period, Tax Effect	758	(113)
Amortization of held-to-maturity discount resulting from transfer, Tax Effect	(3)	(3)
Total other comprehensive income (loss), Tax Effect	755	(116)
Ending Balance, Tax Effect	492	(136)
Beginning balance, After-tax	986	72
Unrealized holding gain (loss) on available-for-sale securities arising during the period, After-Tax	(2,849)	427
Amortization of held-to-maturity discount resulting from transfer, After-tax	13	11
Other comprehensive income (loss)	(2,836)	438
Ending Balance, After-tax	$ (1,850)	$ 510