Revenue Recognition - Summary of Revenues Disaggregated by Geography (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation Of Revenue [Line Items]
Total revenue		$ 50,212	$ 61,647	$ 98,761	$ 120,370
UNITED STATES
Disaggregation Of Revenue [Line Items]
Total revenue		34,225	45,327	67,102	89,945
Other
Disaggregation Of Revenue [Line Items]
Total revenue	[1]	$ 15,987	$ 16,320	$ 31,659	$ 30,425

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