Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Selected Quarterly Financial Data (Unaudited)
Revenue	$ 383,840	$ 410,565	$ 416,567	$ 369,547	$ 356,468	$ 370,145	$ 362,801	$ 321,381	$ 1,580,519	$ 1,410,795	$ 1,357,272
Gross profit	83,927	87,465	82,049	64,688	69,304	66,459	61,859	52,149	318,129	249,771	239,883
Net income including noncontrolling interests	14,883	19,886	15,782	6,889	11,821	9,379	6,336	1,063	57,440	28,599	28,556
Net income attributable to Comfort Systems USA, Inc.	$ 13,221	$ 17,673	$ 13,404	$ 5,066	$ 10,682	$ 7,605	$ 4,401	$ 375	$ 49,364	$ 23,063	$ 27,269
Basic-
Income from continuing operations (in dollars per share)	$ 0.35	$ 0.47	$ 0.36	$ 0.14	$ 0.29	$ 0.20	$ 0.12	$ 0.01	$ 1.32	$ 0.61	$ 0.73
Net income (in dollars per share)	0.35	0.47	0.36	0.14	0.29	0.20	0.12	0.01	1.32	0.61	0.73
Diluted-
Income from continuing operations (in dollars per share)	0.35	0.46	0.35	0.13	0.29	0.20	0.12	0.01	1.30	0.61	0.73
Net income (in dollars per share)	$ 0.35	$ 0.46	$ 0.35	$ 0.13	$ 0.29	$ 0.20	$ 0.12	$ 0.01	$ 1.30	$ 0.61	$ 0.73
Project gain (loss)	$ 3,400								$ 3,400	$ (4,400)