Revenue - Disaggregation of Revenue by Revenue Source and Pattern of Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 192,820	$ 157,678	$ 546,297	$ 449,579
Over Time
Disaggregation of Revenue [Line Items]
Revenues	191,935	156,218	543,341	446,297
Point In Time
Disaggregation of Revenue [Line Items]
Revenues	885	1,460	2,956	3,282
Services
Disaggregation of Revenue [Line Items]
Revenues	192,419	156,755	544,924	447,993
Services | Over Time
Disaggregation of Revenue [Line Items]
Revenues	191,935	156,218	543,341	446,297
Services | Point In Time
Disaggregation of Revenue [Line Items]
Revenues	484	537	1,583	1,696
Professional services
Disaggregation of Revenue [Line Items]
Revenues	189,241	152,850	534,650	435,983
Professional services | Over Time
Disaggregation of Revenue [Line Items]
Revenues	189,241	152,850	534,650	435,983
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	146,675	114,581	414,540	316,866
Professional services | Time and materials contracts | Over Time
Disaggregation of Revenue [Line Items]
Revenues	146,675	114,581	414,540	316,866
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	11,572	13,920	35,252	39,556
Professional services | Fixed fee percent complete contracts | Over Time
Disaggregation of Revenue [Line Items]
Revenues	11,572	13,920	35,252	39,556
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	28,678	22,836	77,726	72,124
Professional services | Fixed fee contracts | Over Time
Disaggregation of Revenue [Line Items]
Revenues	28,678	22,836	77,726	72,124
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	2,316	1,513	7,132	7,437
Professional services | Reimbursable expenses | Over Time
Disaggregation of Revenue [Line Items]
Revenues	2,316	1,513	7,132	7,437
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	3,178	3,905	10,274	12,010
Other services | Over Time
Disaggregation of Revenue [Line Items]
Revenues	2,694	3,368	8,691	10,314
Other services | Point In Time
Disaggregation of Revenue [Line Items]
Revenues	484	537	1,583	1,696
Software and hardware
Disaggregation of Revenue [Line Items]
Revenues	401	923	1,373	1,586
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	$ 401	$ 923	$ 1,373	$ 1,586