Revenue - Disaggregation of Revenue by Revenue Source and Pattern of Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Revenues	$ 231,105	$ 222,738	$ 462,513	$ 444,849
Over Time
Disaggregation of Revenue [Line Items]
Revenues	230,100	221,600	460,600	442,700
Point In Time
Disaggregation of Revenue [Line Items]
Revenues	1,000	1,100	1,900	2,100
Services
Disaggregation of Revenue [Line Items]
Revenues	230,700	222,300	461,600	443,700
Services | Over Time
Disaggregation of Revenue [Line Items]
Revenues	230,100	221,600	460,600	442,700
Services | Point In Time
Disaggregation of Revenue [Line Items]
Revenues	600	700	1,000	1,000
Professional services
Disaggregation of Revenue [Line Items]
Revenues	228,600	219,600	457,700	438,800
Professional services | Over Time
Disaggregation of Revenue [Line Items]
Revenues	228,600	219,600	457,700	438,800
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	170,600	170,600	346,100	342,200
Professional services | Time and materials contracts | Over Time
Disaggregation of Revenue [Line Items]
Revenues	170,600	170,600	346,100	342,200
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	16,200	13,500	31,000	27,900
Professional services | Fixed fee percent complete contracts | Over Time
Disaggregation of Revenue [Line Items]
Revenues	16,200	13,500	31,000	27,900
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	39,700	33,100	76,000	64,300
Professional services | Fixed fee contracts | Over Time
Disaggregation of Revenue [Line Items]
Revenues	39,700	33,100	76,000	64,300
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	2,100	2,400	4,600	4,400
Professional services | Reimbursable expenses | Over Time
Disaggregation of Revenue [Line Items]
Revenues	2,100	2,400	4,600	4,400
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	2,100	2,700	3,900	4,900
Other services | Over Time
Disaggregation of Revenue [Line Items]
Revenues	1,500	2,000	2,900	3,900
Other services | Point In Time
Disaggregation of Revenue [Line Items]
Revenues	600	700	1,000	1,000
Software and hardware
Disaggregation of Revenue [Line Items]
Revenues	400	400	900	1,100
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	$ 400	$ 400	$ 900	$ 1,100