Reportable Segments - Reconciliation of Segment Operating Income (Loss) (Details) (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
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]                      
Gross Profit $ 13,177 $ 47,978 $ 13,729 $ 8,280 $ 23,164 $ 46,185 $ 17,490 $ 9,274 $ 83,164 $ 96,113 $ 61,419
Operating expenses, net                 (60,834) (49,121) (27,986)
Total operating income                 22,330 46,992 33,433
Operating Segments | Government gross profit                      
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]                      
Gross Profit                 161,809 146,149 64,636
Operating Segments | Commercial gross profit                      
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]                      
Gross Profit                 55,382 53,541 42,904
Non-allocated costs                      
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]                      
Non-allocated costs of revenue                 (134,027) [1] (103,577) [1] (46,121) [1]
Operating expenses, net                 $ (60,834) [2] $ (49,121) [2] $ (27,986) [2]
[1] Non-allocated costs include costs that are shared by both of the reporting segments but are not allocated to the operating segments for the use of the CODM and expenses that are not directly attributable to the operating segments.
[2] Other corporate expenses include research and development, corporate sales and marketing expenses, stock-based compensation expense, certain tax expenses, various nonrecurring charges, and other separately managed general and administrative costs.