Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Accrued salaries, benefits and bonus	$ 8,957	$ 6,474
Accrued professional, consulting and lobbying fees	3,870	3,673
Accrued warranty expense	644	780	$ 314	$ 675
Accrued income and other taxes	2,558	4,581
Other accrued expenses	7,473	2,740
Accrued liabilities	$ 23,502	$ 18,248