Loans - Composition of Nonaccrual Loans and Impaired Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
Loans on nonaccrual	$ 1,084	$ 2,336	$ 4,146
Loans 90 days past due and still accruing	0	0	0
Impaired loans on nonaccrual included above	304	332	3,031
Total recorded investment in impaired loans	3,830	3,225	6,327
Average recorded investment of impaired loans	3,661	4,490	7,434
Accruing troubled debt restructures	3,526	2,893	3,296
Interest income not recorded on nonaccrual loans according to their original terms	37	91	123
Interest income on nonaccrual loans actually recorded	0	0	0
Interest income recognized on impaired loans	$ 140	$ 104	$ 144