Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2015	Oct. 23, 2015	Dec. 31, 2014
Document and Entity Information
Entity Registrant Name	COMFORT SYSTEMS USA INC
Entity Central Index Key	0001035983
Document Type	10-Q
Document Period End Date	Sep. 30, 2015
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		37,449,352
Treasury Stock, Shares	3,637,011	3,674,013	3,853,586
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q3