Condensed Consolidated Statements Of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Revenues	$ 2,437,666	$ 2,014,021	$ 4,741,715	$ 4,313,853
Cost of sales	2,061,387	1,698,735	4,024,363	3,665,506
Gross profit	376,279	315,286	717,352	648,347
Selling, general and administrative expenses	242,921	205,174	466,990	432,171
Restructuring expenses	0	0	0	69
Impairment loss on goodwill, identifiable intangible assets, and other long-lived assets	0	232,750	0	232,750
Operating income (loss)	133,358	(122,638)	250,362	(16,643)
Net periodic pension (cost) income	922	718	1,830	1,460
Interest expense, net	(1,316)	(2,110)	(2,679)	(4,598)
Income (loss) before income taxes	132,964	(124,030)	249,513	(19,781)
Income tax provision (benefit)	35,616	(40,341)	67,220	(11,757)
Net income (loss) including noncontrolling interests	97,348	(83,689)	182,293	(8,024)
Net (loss) income attributable to noncontrolling interests	(2)	0	169	0
Net income (loss) attributable to EMCOR Group, Inc. (in US dollars)	$ 97,350	$ (83,689)	$ 182,124	$ (8,024)
Basic earnings (loss) per common share (in US dollars per share)	$ 1.79	$ (1.52)	$ 3.34	$ (0.14)
Diluted earnings (loss) per common share (in US dollars per share)	1.78	(1.52)	3.32	(0.14)
Dividends declared per common share (in US dollars per share)	$ 0.13	$ 0.08	$ 0.26	$ 0.16