Other Income and Expenses - Other Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Income and Expenses [Abstract]
Other service charges, commissions and fees	$ 99	$ 116	$ 109
Rentals	298	320	393
Other	84	223	212
Totals	$ 481	$ 659	$ 714