Loans - Schedule of Average Recorded Investment in Impaired Loans and Related Interest Income Recognized (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Average recorded investment:
Average recorded investment in impaired loans	$ 5,864	$ 4,171
Interest income recognized:
Interest income recognized on a cash basis on impaired loans	30	28
Commercial [Member]
Average recorded investment:
Average recorded investment in impaired loans	2,453	861
Interest income recognized:
Interest income recognized on a cash basis on impaired loans	18	13
Commercial Real Estate [Member]
Average recorded investment:
Average recorded investment in impaired loans	2,556	2,289
Interest income recognized:
Interest income recognized on a cash basis on impaired loans	2	3
Residential Real Estate [Member]
Average recorded investment:
Average recorded investment in impaired loans	846	1,018
Interest income recognized:
Interest income recognized on a cash basis on impaired loans	10	12
Consumer [Member]
Average recorded investment:
Average recorded investment in impaired loans	$ 9	$ 3