Warranty Costs - Changes in Carrying Amount of Accrued Product Warranty Costs (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	$ 9,158	$ 9,468
Accrued current period warranty expense	355	930
Payments and adjustments	(1,161)	(1,161)
Balance at end of period	$ 8,352	$ 9,237