Other Real Estate Owned and Other Repossessed Assets - Expenses Related to Foreclosed and Repossessed Assets (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Other Real Estate And Foreclosed Assets [Abstract]
Net loss on sales	$ 103,000	$ 18,000	$ 158,000	$ 108,000
Provision for (recovery of) unrealized losses	10,000	0	33,000	(38,000)
Operating expenses, net of rental income	34,000	23,000	70,000	85,000
Total expenses	$ 147,000	$ 41,000	$ 261,000	$ 155,000