Industry and Geographic Information - Long-lived Assets (Excluding Intangible Assets) and Total Net Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, Total	$ 50,858				$ 52,547				$ 50,858	$ 52,547
Total revenues	52,808	$ 49,341	$ 39,133	$ 50,321	52,412	$ 46,812	$ 35,204	$ 61,701	191,603	196,129	$ 184,158
Federal [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, Total	50,774				52,426				50,774	52,426
Total revenues									158,244	168,809	159,845
Foreign [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, Total	$ 84				$ 121				84	121
Total revenues									$ 33,359	$ 27,320	$ 24,313