Loans - Schedule of Average Recorded Investment in Impaired Loans and Related Interest Income Recognized (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Average recorded investment:
Average recorded investment in impaired loans	$ 5,988	$ 4,692	$ 5,926	$ 4,456
Interest income recognized:
Interest income recognized on a cash basis on impaired loans	33	43	63	66
Commercial [Member]
Average recorded investment:
Average recorded investment in impaired loans	2,523	1,582	2,488	1,228
Interest income recognized:
Interest income recognized on a cash basis on impaired loans	19	28	37	37
Commercial Real Estate [Member]
Average recorded investment:
Average recorded investment in impaired loans	2,550	2,152	2,553	2,233
Interest income recognized:
Interest income recognized on a cash basis on impaired loans	4	3	6	6
Residential Real Estate [Member]
Average recorded investment:
Average recorded investment in impaired loans	820	943	833	986
Interest income recognized:
Interest income recognized on a cash basis on impaired loans	9	12	19	23
Consumer [Member]
Average recorded investment:
Average recorded investment in impaired loans	95	$ 15	52	$ 9
Interest income recognized:
Interest income recognized on a cash basis on impaired loans	$ 1		$ 1