Net Revenues by Geographic Location (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenue	$ 35,200	$ 43,100	$ 43,400	$ 30,600	$ 51,200	$ 50,200	$ 43,100	$ 27,600	$ 152,312	$ 172,121	$ 129,656
United States
Segment Reporting Information [Line Items]
Revenue									152,200	172,000	129,300
Other
Segment Reporting Information [Line Items]
Revenue									$ 100	$ 100	$ 400