Revenue - Disaggregation of Revenue by Revenue Source and Pattern of Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 146,339	$ 141,869	$ 291,901	$ 275,684
Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	145,415	140,367	290,079	272,642
Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues	924	1,502	1,822	3,042
Services
Disaggregation of Revenue [Line Items]
Revenues	145,836	141,234	291,238	274,100
Services | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	145,415	140,367	290,079	272,642
Services | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues	421	867	1,159	1,458
Professional Services
Disaggregation of Revenue [Line Items]
Revenues	142,099	136,843	283,133	265,773
Professional Services | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	142,099	136,843	283,133	265,773
Professional Services | Transferred at 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	102,294	96,084	202,285	184,462
Professional Services | Time and materials contracts | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	102,294	96,084	202,285	184,462
Professional Services | Time and materials contracts | Transferred at 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	14,015	10,414	25,636	22,872
Professional Services | Fixed fee percent complete contracts | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	14,015	10,414	25,636	22,872
Professional Services | Fixed fee percent complete contracts | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Professional Services | Fixed fee contracts
Disaggregation of Revenue [Line Items]
Revenues	24,260	25,955	49,288	50,135
Professional Services | Fixed fee contracts | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	24,260	25,955	49,288	50,135
Professional Services | Fixed fee contracts | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Professional Services | Reimbursable expenses
Disaggregation of Revenue [Line Items]
Revenues	1,530	4,390	5,924	8,304
Professional Services | Reimbursable expenses | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	1,530	4,390	5,924	8,304
Professional Services | Reimbursable expenses | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Other Services
Disaggregation of Revenue [Line Items]
Revenues	3,737	4,391	8,105	8,327
Other Services | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	3,316	3,524	6,946	6,869
Other Services | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues	421	867	1,159	1,458
Software and hardware
Disaggregation of Revenue [Line Items]
Revenues	503	635	663	1,584
Software and hardware | Transferred over Time
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Software and hardware | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Revenues	$ 503	$ 635	$ 663	$ 1,584