Revenue - Disaggregation of Revenue by Revenue Source and Pattern of Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 184,136	$ 146,339	$ 353,477	$ 291,901
Over Time
Disaggregation of Revenue [Line Items]
Revenues	183,387	145,415	351,406	290,079
Point In Time
Disaggregation of Revenue [Line Items]
Revenues	749	924	2,071	1,822
Services
Disaggregation of Revenue [Line Items]
Revenues	183,775	145,836	352,505	291,238
Services | Over Time
Disaggregation of Revenue [Line Items]
Revenues	183,387	145,415	351,406	290,079
Services | Point In Time
Disaggregation of Revenue [Line Items]
Revenues	388	421	1,099	1,159
Professional services
Disaggregation of Revenue [Line Items]
Revenues	180,507	142,099	345,409	283,133
Professional services | Over Time
Disaggregation of Revenue [Line Items]
Revenues	180,507	142,099	345,409	283,133
Professional services | Point In Time
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Professional services | Time and materials contracts
Disaggregation of Revenue [Line Items]
Revenues	139,274	102,294	267,865	202,285
Professional services | Time and materials contracts | Over Time
Disaggregation of Revenue [Line Items]
Revenues	139,274	102,294	267,865	202,285
Professional services | Time and materials contracts | Point In Time
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Professional services | Fixed fee percent complete contracts
Disaggregation of Revenue [Line Items]
Revenues	12,100	14,015	23,680	25,636
Professional services | Fixed fee percent complete contracts | Over Time
Disaggregation of Revenue [Line Items]
Revenues	12,100	14,015	23,680	25,636
Professional services | Fixed fee percent complete contracts | Point In Time
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Professional services | Fixed fee contracts
Disaggregation of Revenue [Line Items]
Revenues	26,571	24,260	49,048	49,288
Professional services | Fixed fee contracts | Over Time
Disaggregation of Revenue [Line Items]
Revenues	26,571	24,260	49,048	49,288
Professional services | Fixed fee contracts | Point In Time
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Professional services | Reimbursable expenses
Disaggregation of Revenue [Line Items]
Revenues	2,562	1,530	4,816	5,924
Professional services | Reimbursable expenses | Over Time
Disaggregation of Revenue [Line Items]
Revenues	2,562	1,530	4,816	5,924
Professional services | Reimbursable expenses | Point In Time
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Other services
Disaggregation of Revenue [Line Items]
Revenues	3,268	3,737	7,096	8,105
Other services | Over Time
Disaggregation of Revenue [Line Items]
Revenues	2,880	3,316	5,997	6,946
Other services | Point In Time
Disaggregation of Revenue [Line Items]
Revenues	388	421	1,099	1,159
Software and hardware
Disaggregation of Revenue [Line Items]
Revenues	361	503	972	663
Software and hardware | Over Time
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Software and hardware | Point In Time
Disaggregation of Revenue [Line Items]
Revenues	$ 361	$ 503	$ 972	$ 663