Revenue - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Disaggregation of Revenue
Revenue recognized	$ 130,053	$ 118,365	$ 400,655	$ 381,835
Contract with customer, assets	41,164		41,164		$ 37,843
Contract with customer, liability	4,840		4,840		$ 1,324
Contract assets transferred to receivables			20,561
Cash proceeds from liability contract			4,512
Revenue recognized from contract liability	$ 81	$ 175	$ 985	$ 3,708
Over time
Disaggregation of Revenue
Customer revenue transferred (percentage)	35.80%	32.20%	29.70%	27.90%
Revenue recognized	$ 46,576	$ 38,116	$ 119,122	$ 106,439
Over time | Performance Based
Disaggregation of Revenue
Revenue recognized	30,314	27,316	79,109	76,606
Over time | Delivery Based
Disaggregation of Revenue
Revenue recognized	$ 16,262	$ 10,800	$ 40,013	$ 29,833
Point in time
Disaggregation of Revenue
Customer revenue transferred (percentage)	64.20%	67.80%	70.30%	72.10%
Revenue recognized	$ 83,477	$ 80,249	$ 281,533	$ 275,396