Document and Entity Information	9 Months Ended
	Sep. 30, 2013	Oct. 23, 2013	Dec. 31, 2012
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, 2013
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		37,355,508
Treasury Stock, Shares	3,767,857	3,767,857	3,879,299
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q3