Qualified Affordable Housing Project Investments - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Investments in Affordable Housing Projects [Abstract]
Investment for qualified affordable housing projects included in other assets	$ 2,267,000		$ 2,177,000
Unfunded commitments related to the investments in qualified affordable housing projects	2,027,000		$ 2,195,000
Recognized amortization expense included in pretax income	77,000	$ 69,000
Recognized tax credits and other benefits from its investment in affordable housing tax credits	147,000	117,000
Impairment losses related to its investment in qualified affordable housing projects	$ 0	$ 0