Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator
Income from continuing operations attributable to EMCOR Group, Inc. common stockholders (in US dollars)	$ 64,804	$ 51,937	$ 174,724	$ 142,843
Loss from discontinued operation, net of income taxes (in US dollars)	(207)	(406)	(729)	(1,584)
Net income attributable to EMCOR Group, Inc. (in US dollars)	$ 64,597	$ 51,531	$ 173,995	$ 141,259
Denominator
Weighted average shares outstanding used to compute basic earnings (loss) per common share (in shares)	59,061,768	60,889,484	59,371,672	60,866,532
Effect of dilutive securities-Share-based awards (in shares)	357,432	428,573	349,513	423,856
Shares used to compute diluted earnings (loss) per common share (in shares)	59,419,200	61,318,057	59,721,185	61,290,388
Basic earnings (loss) per common share:
From continuing operations attributable to EMCOR Group, Inc. common stockholders (in US dollars per share)	$ 1.10	$ 0.85	$ 2.94	$ 2.35
From discontinued operation (in US dollars per share)	0.00	(0.01)	(0.01)	(0.03)
Net income attributable to EMCOR Group, Inc. common stockholders (in US dollars per share)	1.10	0.84	2.93	2.32
Diluted earnings (loss) per common share:
From continuing operations attributable to EMCOR Group, Inc. common stockholders (in US dollars per share)	1.09	0.85	2.93	2.33
From discontinued operation (in US dollars per share)	0.00	(0.01)	(0.01)	(0.03)
Net income attributable to EMCOR Group, Inc. common stockholders (in US dollars per share)	$ 1.09	$ 0.84	$ 2.92	$ 2.30
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive share-based awards excluded from calculation of diluted earnings per share (in shares)	500	0	500	0