Revenues - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 214,730	$ 192,820	$ 184,136	$ 169,341	$ 162,554	$ 157,678	$ 146,339	$ 145,562	$ 761,027	$ 612,133	$ 565,527
Transferred Over Time
Disaggregation of Revenue [Line Items]
Revenues									756,486	607,101	559,040
Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues									4,541	5,032	6,487
Professional Services
Disaggregation of Revenue [Line Items]
Revenues									745,166	593,565	545,436
Professional Services | Transferred Over Time
Disaggregation of Revenue [Line Items]
Revenues									745,166	593,565	545,436
Professional Services | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Professional Services | Time and materials contracts
Disaggregation of Revenue [Line Items]
Revenues									577,674	436,466	384,422
Professional Services | Time and materials contracts | Transferred Over Time
Disaggregation of Revenue [Line Items]
Revenues									577,674	436,466	384,422
Professional Services | Time and materials contracts | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Professional Services | Fixed fee percent complete contracts
Disaggregation of Revenue [Line Items]
Revenues									49,117	51,752	41,484
Professional Services | Fixed fee percent complete contracts | Transferred Over Time
Disaggregation of Revenue [Line Items]
Revenues									49,117	51,752	41,484
Professional Services | Fixed fee percent complete contracts | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Professional Services | Fixed fee contracts
Disaggregation of Revenue [Line Items]
Revenues									107,698	95,237	104,056
Professional Services | Fixed fee contracts | Transferred Over Time
Disaggregation of Revenue [Line Items]
Revenues									107,698	95,237	104,056
Professional Services | Fixed fee contracts | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Professional Services | Reimbursable expenses
Disaggregation of Revenue [Line Items]
Revenues									10,677	10,110	15,474
Professional Services | Reimbursable expenses | Transferred Over Time
Disaggregation of Revenue [Line Items]
Revenues									10,677	10,110	15,474
Professional Services | Reimbursable expenses | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Other Services
Disaggregation of Revenue [Line Items]
Revenues									13,556	16,018	16,482
Other Services | Transferred Over Time
Disaggregation of Revenue [Line Items]
Revenues									11,320	13,536	13,604
Other Services | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues									2,236	2,482	2,878
Total services
Disaggregation of Revenue [Line Items]
Revenues									758,722	609,583	561,918
Total services | Transferred Over Time
Disaggregation of Revenue [Line Items]
Revenues									756,486	607,101	559,040
Total services | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues									2,236	2,482	2,878
Software and hardware
Disaggregation of Revenue [Line Items]
Revenues									2,305	2,550	3,609
Software and hardware | Transferred Over Time
Disaggregation of Revenue [Line Items]
Revenues									0	0	0
Software and hardware | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues									2,305	2,550	3,609
United States
Disaggregation of Revenue [Line Items]
Revenues									738,298	599,236	552,357
Other countries
Disaggregation of Revenue [Line Items]
Revenues									$ 22,729	$ 12,897	$ 13,170