Accounting for Certain Loans Acquired in a Transfer - Additional Information (Detail) - USD ($)	3 Months Ended							12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Total provision charged to operating expense	$ 342,000	$ 300,000	$ 1,906,000	$ 614,000	$ 978,000	$ 1,741,000	$ 339,000	$ 3,162,000	$ 3,058,000	$ 1,920,000
Loans Purchased With Evidence Of Credit Deterioration [Member]
Business Acquisition [Line Items]
Total provision charged to operating expense									(190,000)	253,000
Allowances for loan losses									$ 63,000	$ 283,000