Revenue - Disaggregation of revenue by customer type and contract type (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue
Revenue	$ 1,284,128	$ 913,245	$ 3,091,461	$ 2,613,184
Fixed price
Disaggregation of Revenue
Revenue	498,643	314,468	1,203,811	927,195
Unit price
Disaggregation of Revenue
Revenue	549,705	378,237	1,329,367	1,078,805
Cost reimbursable
Disaggregation of Revenue
Revenue	235,780	220,540	558,283	607,184
MSA
Disaggregation of Revenue
Revenue	605,847	466,631	1,451,390	1,218,094
Non-MSA
Disaggregation of Revenue
Revenue	678,281	446,614	1,640,071	1,395,090
Utilities
Disaggregation of Revenue
Revenue	613,008	454,654	1,447,857	1,215,087
Utilities | Fixed price
Disaggregation of Revenue
Revenue	58,602	33,280	123,742	90,142
Utilities | Unit price
Disaggregation of Revenue
Revenue	397,204	311,191	988,477	844,314
Utilities | Cost reimbursable
Disaggregation of Revenue
Revenue	157,202	110,183	335,638	280,631
Utilities | MSA
Disaggregation of Revenue
Revenue	516,363	410,041	1,226,511	1,039,743
Utilities | Non-MSA
Disaggregation of Revenue
Revenue	96,645	44,613	221,346	175,344
Energy/Renewables
Disaggregation of Revenue
Revenue	600,444	351,026	1,445,843	1,038,900
Energy/Renewables | Fixed price
Disaggregation of Revenue
Revenue	391,887	212,956	930,271	564,552
Energy/Renewables | Unit price
Disaggregation of Revenue
Revenue	140,361	65,904	327,624	231,715
Energy/Renewables | Cost reimbursable
Disaggregation of Revenue
Revenue	68,196	72,166	187,948	242,633
Energy/Renewables | MSA
Disaggregation of Revenue
Revenue	56,493	41,133	153,178	126,997
Energy/Renewables | Non-MSA
Disaggregation of Revenue
Revenue	543,951	309,893	1,292,665	911,903
Pipeline
Disaggregation of Revenue
Revenue	70,676	107,565	197,761	359,197
Pipeline | Fixed price
Disaggregation of Revenue
Revenue	48,154	68,232	149,798	272,501
Pipeline | Unit price
Disaggregation of Revenue
Revenue	12,140	1,142	13,266	2,776
Pipeline | Cost reimbursable
Disaggregation of Revenue
Revenue	10,382	38,191	34,697	83,920
Pipeline | MSA
Disaggregation of Revenue
Revenue	32,991	15,457	71,701	51,354
Pipeline | Non-MSA
Disaggregation of Revenue
Revenue	$ 37,685	$ 92,108	$ 126,060	$ 307,843