Retirement Plans - Schedule of Amounts Recognized in Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net (gain) loss	$ (225)	$ (10)	$ (76)
Transition obligation	0	0	0
Total	(225)	$ (10)	$ (76)
Postretirement Benefit Costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net (gain) loss	21
Transition obligation	0
Total	$ 21