Selected Unaudited Quarterly Information (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2009
Selected Unaudited Quarterly Information [Abstract]
Revenues	$ 1,517,962	$ 1,482,241	$ 1,348,013	$ 1,265,243	$ 1,300,735	$ 1,220,083	$ 1,197,181	$ 1,133,954	$ 5,613,459		$ 4,851,953	$ 5,227,699
Gross profit	214,317	188,267	174,656	156,709	201,476	171,445	166,031	154,571	733,949		693,523	784,225
Impairment loss on goodwill and identifiable intangible assets	3,795					226,152	19,929		3,795		246,081	13,526
Net income (loss) attributable to EMCOR Group, Inc.	$ 36,665	$ 40,758	$ 28,809	$ 24,594	$ 39,976	$ (175,625)	$ 27,141	$ 21,817	$ 130,826		$ (86,691)	$ 160,756
Basic EPS from continuing operations	$ 0.54	$ 0.48	$ 0.44	$ 0.36	$ 0.63	$ (2.60)	$ 0.38	$ 0.30	$ 1.82		$ (1.30)	$ 2.31
Basic EPS from discontinued operation	$ 0.01	$ 0.13	$ (0.01)	$ 0.01	$ (0.03)	$ (0.04)	$ 0.03	$ 0.03	$ 0.14		$ (0.01)	$ 0.13
Earnings per share, basic	$ 0.55	$ 0.61	$ 0.43	$ 0.37	$ 0.60	$ (2.64)	$ 0.41	$ 0.33	$ 1.96		$ (1.31)	$ 2.44
Diluted EPS from continuing operations	$ 0.53	$ 0.47	$ 0.43	$ 0.35	$ 0.61	$ (2.60)	$ 0.37	$ 0.29	$ 1.78		$ (1.30)	$ 2.25
Diluted EPS from discontinued operation	$ 0.01	$ 0.13	$ (0.01)	$ 0.01	$ (0.02)	$ (0.04)	$ 0.03	$ 0.03	$ 0.13	[1]	$ (0.01)	$ 0.13
Earnings per share, diluted	$ 0.54	$ 0.60	$ 0.42	$ 0.36	$ 0.59	$ (2.64)	$ 0.40	$ 0.32	$ 1.91		$ (1.31)	$ 2.38

[1] Through the date of sale, August 2, 2011.