Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2016	Oct. 21, 2016
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, 2016
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		37,209,358
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q3