Geographical Information - Revenue by Geographical Area (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 182,424	$ 195,737	$ 550,880	$ 578,948
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	126,412	131,542	375,595	379,103
All Other Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 56,012	$ 64,195	$ 175,285	$ 199,845