Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Selected Quarterly Financial Information [Abstract]
Revenue	$ 392,100	$ 428,760	$ 427,538	$ 385,942	$ 383,840	$ 410,565	$ 416,567	$ 369,547	$ 1,634,340	$ 1,580,519	$ 1,410,795
Gross Profit	88,265	92,816	89,426	73,502	83,927	87,465	82,049	64,688	344,009	318,129	249,771
Net income including noncontrolling interests	16,867	20,471	17,717	9,841	14,883	19,886	15,782	6,889	64,896	57,440	28,599
Net income attributable to Comfort Systems USA, Inc.	$ 16,867	$ 20,471	$ 17,717	$ 9,841	$ 13,221	$ 17,673	$ 13,404	$ 5,066	$ 64,896	$ 49,364	$ 23,063
Basic-
Income from continuing operations (in dollars per share)	$ 0.45	$ 0.55	$ 0.47	$ 0.26	$ 0.35	$ 0.47	$ 0.36	$ 0.14	$ 1.74	$ 1.32	$ 0.61
Net income (in dollars per share)	0.45	0.55	0.47	0.26	0.35	0.47	0.36	0.14	1.74	1.32	0.61
Diluted-
Income from continuing operations (in dollars per share)	0.45	0.54	0.47	0.26	0.35	0.46	0.35	0.13	1.72	1.30	0.61
Net income (in dollars per share)	$ 0.45	$ 0.54	$ 0.47	$ 0.26	$ 0.35	$ 0.46	$ 0.35	$ 0.13	$ 1.72	$ 1.30	$ 0.61
Gain Loss From Project					$ 3,400					$ 3,400	$ 4,400