Accrued Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Accrued salaries, benefits and bonus	$ 12,527		$ 8,957
Accrued professional, consulting and lobbying fees	2,683		3,870
Accrued warranty expense	505		644	$ 564	$ 780
Accrued income and other taxes	2,894		2,558
Other accrued liabilities	11,386		7,473
Accrued liabilities	$ 29,995	$ 26,014	$ 23,502