Other Real Estate Owned and Other Repossessed Assets - Valuation Allowance Related to Real Estate Owned (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Other Real Estate And Foreclosed Assets [Abstract]
Beginning of period	$ 549,000	$ 1,124,000	$ 1,012,000	$ 1,229,000
Recovery of expense	0	(27,000)	(38,000)	(26,000)
Reductions due to sales	(160,000)	(96,000)	(585,000)	(202,000)
End of period	$ 389,000	$ 1,001,000	$ 389,000	$ 1,001,000