Accounting for Certain Loans Acquired in a Transfer - Additional Information (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Total provision charged to operating expense	$ 623,000	$ 455,000	$ 232,000	$ 532,000	$ 342,000	$ 300,000	$ 1,906,000	$ 614,000	$ 1,842,000	$ 3,162,000	$ 3,058,000
Loans Purchased With Evidence of Credit Deterioration [Member]
Business Acquisition [Line Items]
Total provision charged to operating expense									71,000	(190,000)
Allowances for loan losses									$ 0	$ 63,000