Segment Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) segment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Segment Information
Number of reportable segments | segment	2
Revenue	$ 3,073,636	$ 2,856,659	$ 2,615,277
Gross Profit	563,207	546,983	501,943
Capital Expenditures	22,330	24,131	31,750
Total Assets	2,209,114	1,757,355
Operating | Mechanical Services
Segment Information
Revenue	2,542,623	2,430,632	2,272,031
Gross Profit	486,346	513,760	469,347
Capital Expenditures	19,408	22,561	28,070
Total Assets	1,452,527	1,246,098
Operating | Electrical Services
Segment Information
Revenue	531,013	426,027	343,246
Gross Profit	76,861	33,223	32,596
Capital Expenditures	2,413	944	1,367
Total Assets	690,364	419,475
Corporate & Eliminations
Segment Information
Capital Expenditures	509	626	$ 2,313
Total Assets	$ 66,223	$ 91,782