Revenue - Disaggregation of revenue by customer type and contract type (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue
Revenue	$ 1,529,486	$ 1,284,128	$ 4,199,760	$ 3,091,461
Fixed price
Disaggregation of Revenue
Revenue	642,254	498,643	1,838,526	1,203,811
Unit price
Disaggregation of Revenue
Revenue	574,514	549,705	1,577,748	1,329,367
Cost reimbursable
Disaggregation of Revenue
Revenue	312,718	235,780	783,486	558,283
MSA
Disaggregation of Revenue
Revenue	584,026	605,847	1,577,291	1,451,390
Non-MSA
Disaggregation of Revenue
Revenue	945,460	678,281	2,622,469	1,640,071
Utilities
Disaggregation of Revenue
Revenue	644,639	613,008	1,813,768	1,447,857
Utilities | Fixed price
Disaggregation of Revenue
Revenue	106,267	58,602	290,320	123,742
Utilities | Unit price
Disaggregation of Revenue
Revenue	406,368	397,204	1,131,044	988,477
Utilities | Cost reimbursable
Disaggregation of Revenue
Revenue	132,004	157,202	392,404	335,638
Utilities | MSA
Disaggregation of Revenue
Revenue	505,301	516,363	1,354,642	1,226,511
Utilities | Non-MSA
Disaggregation of Revenue
Revenue	139,338	96,645	459,126	221,346
Energy
Disaggregation of Revenue
Revenue	884,847	671,120	2,385,992	1,643,604
Energy | Fixed price
Disaggregation of Revenue
Revenue	535,987	440,041	1,548,206	1,080,069
Energy | Unit price
Disaggregation of Revenue
Revenue	168,146	152,501	446,704	340,890
Energy | Cost reimbursable
Disaggregation of Revenue
Revenue	180,714	78,578	391,082	222,645
Energy | MSA
Disaggregation of Revenue
Revenue	78,725	89,484	222,649	224,879
Energy | Non-MSA
Disaggregation of Revenue
Revenue	$ 806,122	$ 581,636	$ 2,163,343	$ 1,418,725