Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Oct. 24, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	1-8267
Entity Registrant Name	EMCOR Group, Inc.
Entity Central Index Key	0000105634
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	11-2125338
Entity Address, Address Line One	301 Merritt Seven
Entity Address, City or Town	Norwalk,
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06851-1092
City Area Code	(203)
Local Phone Number	849-7800
Title of 12(b) Security	Common Stock
Trading Symbol	EME
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		56,153,125