Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) segment	Jun. 30, 2020 USD ($)
Segment Information
Number of reportable segments | segment			2
Revenue	$ 713,895	$ 743,468	$ 1,383,656	$ 1,443,599
Gross Profit	126,455	145,695	249,924	262,788
Operating | Mechanical Services Segment
Segment Information
Revenue	611,796	626,706	1,177,416	1,197,457
Gross Profit	112,405	136,708	220,533	246,692
Operating | Electrical Services
Segment Information
Revenue	102,099	116,762	206,240	246,142
Gross Profit	$ 14,050	$ 8,987	$ 29,391	$ 16,096