Revenue Recognition - Summary of Revenues Disaggregated by Geography (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Disaggregation Of Revenue [Line Items]
Total revenue		$ 48,548	$ 58,722
UNITED STATES
Disaggregation Of Revenue [Line Items]
Total revenue		32,877	44,618
Other
Disaggregation Of Revenue [Line Items]
Total revenue	[1]	$ 15,671	$ 14,104

[1] No single country represented 10% of the Company’s revenues in the periods presented.