Revenue - Disaggregation of Revenue by Revenue Source and Pattern of Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 145,562	$ 133,815
Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	144,664	132,275
Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues	898	1,540
Services
Disaggregation of Revenue [Line Items]
Revenues	145,402	132,866
Services | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	144,664	132,275
Services | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues	738	591
Professional Services
Disaggregation of Revenue [Line Items]
Revenues	141,034	128,930
Professional Services | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	141,034	128,930
Professional Services | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues	0	0
Professional Services | Time and materials contracts
Disaggregation of Revenue [Line Items]
Revenues	99,991	88,378
Professional Services | Time and materials contracts | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	99,991	88,378
Professional Services | Time and materials contracts | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues	0	0
Professional Services | Fixed fee percent complete contracts
Disaggregation of Revenue [Line Items]
Revenues	11,621	12,458
Professional Services | Fixed fee percent complete contracts | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	11,621	12,458
Professional Services | Fixed fee percent complete contracts | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues	0	0
Professional Services | Fixed fee contracts
Disaggregation of Revenue [Line Items]
Revenues	25,028	24,180
Professional Services | Fixed fee contracts | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	25,028	24,180
Professional Services | Fixed fee contracts | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues	0	0
Professional Services | Reimbursable expenses
Disaggregation of Revenue [Line Items]
Revenues	4,394	3,914
Professional Services | Reimbursable expenses | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	4,394	3,914
Professional Services | Reimbursable expenses | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues	0	0
Other Services
Disaggregation of Revenue [Line Items]
Revenues	4,368	3,936
Other Services | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	3,630	3,345
Other Services | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues	738	591
Software and hardware
Disaggregation of Revenue [Line Items]
Revenues	160	949
Software and hardware | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	0	0
Software and hardware | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues	$ 160	$ 949