Industry and Geographic Information - Long-lived Assets (Excluding Intangible Assets) and Total Net Revenue (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, Total	$ 49,226				$ 48,057				$ 49,226	$ 48,057
Total revenues	63,597	40,857	31,488	46,673	50,170	33,539	29,706	61,995	182,615	175,410	155,741
Federal [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, Total	49,052				47,891				49,052	47,891
Total revenues									158,302	152,711	134,239
Foreign [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, Total	174				166				174	166
Total revenues									$ 24,313	$ 22,699	$ 21,502