Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Income from continuing operations attributable to EMCOR Group, Inc. common stockholders (in US dollars)									$ 173,354	$ 146,861	$ 154,388
Loss from discontinued operation, net of income taxes (in US dollars)									(4,690)	(23,069)	(7,804)
Net income attributable to EMCOR Group, Inc. (in US dollars)	$ 42,466us-gaap_NetIncomeLoss	$ 45,024us-gaap_NetIncomeLoss	$ 39,913us-gaap_NetIncomeLoss	$ 41,261us-gaap_NetIncomeLoss	$ 45,921us-gaap_NetIncomeLoss	$ 26,690us-gaap_NetIncomeLoss	$ 21,014us-gaap_NetIncomeLoss	$ 30,167us-gaap_NetIncomeLoss	$ 168,664us-gaap_NetIncomeLoss	$ 123,792us-gaap_NetIncomeLoss	$ 146,584us-gaap_NetIncomeLoss
Weighted average shares outstanding used to compute basic earnings (loss) per common share (in shares)									66,331,886	67,086,299	66,701,869
Effect of dilutive securities-Share-based awards (in shares)									730,623	990,542	1,036,549
Shares used to compute diluted earnings (loss) per common share (in shares)									67,062,509	68,076,841	67,738,418
From continuing operations attributable to EMCOR Group, Inc. common stockholders (in US dollars per share)	$ 0.67	$ 0.68	$ 0.61	$ 0.64	$ 0.77	$ 0.44	$ 0.47	$ 0.51	$ 2.61	$ 2.19	$ 2.32
From discontinued operation (in US dollars per share)	$ (0.01)	$ (0.01)	$ (0.02)	$ (0.03)	$ (0.08)	$ (0.04)	$ (0.16)	$ (0.06)	$ (0.07)	$ (0.34)	$ (0.12)
Net income attributable to EMCOR Group, Inc. common stockholders (in US dollars per share)	$ 0.66us-gaap_EarningsPerShareBasic	$ 0.67us-gaap_EarningsPerShareBasic	$ 0.59us-gaap_EarningsPerShareBasic	$ 0.61us-gaap_EarningsPerShareBasic	$ 0.69us-gaap_EarningsPerShareBasic	$ 0.40us-gaap_EarningsPerShareBasic	$ 0.31us-gaap_EarningsPerShareBasic	$ 0.45us-gaap_EarningsPerShareBasic	$ 2.54us-gaap_EarningsPerShareBasic	$ 1.85us-gaap_EarningsPerShareBasic	$ 2.20us-gaap_EarningsPerShareBasic
From continuing operations attributable to EMCOR Group, Inc. common stockholders (in US dollars per share)	$ 0.66	$ 0.68	$ 0.61	$ 0.64	$ 0.76	$ 0.43	$ 0.47	$ 0.50	$ 2.59	$ 2.16	$ 2.28
From discontinued operation (in US dollars per share)	$ (0.01)	$ (0.01)	$ (0.02)	$ (0.03)	$ (0.08)	$ (0.04)	$ (0.16)	$ (0.06)	$ (0.07)	$ (0.34)	$ (0.12)
Net income attributable to EMCOR Group, Inc. common stockholders (in US dollars per share)	$ 0.65us-gaap_EarningsPerShareDiluted	$ 0.67us-gaap_EarningsPerShareDiluted	$ 0.59us-gaap_EarningsPerShareDiluted	$ 0.61us-gaap_EarningsPerShareDiluted	$ 0.68us-gaap_EarningsPerShareDiluted	$ 0.39us-gaap_EarningsPerShareDiluted	$ 0.31us-gaap_EarningsPerShareDiluted	$ 0.44us-gaap_EarningsPerShareDiluted	$ 2.52us-gaap_EarningsPerShareDiluted	$ 1.82us-gaap_EarningsPerShareDiluted	$ 2.16us-gaap_EarningsPerShareDiluted

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