Quarterly Results of Operations (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Results of Operations (Unaudited)
Revenue	$ 330,340	$ 349,989	$ 351,053	$ 325,890	$ 315,870	$ 335,241	$ 353,172	$ 326,902	$ 1,357,272	$ 1,331,185	$ 1,216,654
Gross profit	61,428	67,021	59,967	51,467	55,073	55,521	54,096	42,931	239,883	207,621	181,530
Operating income	9,059	17,734	14,379	5,086	8,098	9,767	7,441	(3,003)	46,258	22,303	(42,641)
Income from continuing operations	5,932	11,637	8,314	2,749	4,553	5,423	3,949	(2,431)	28,632	11,494	(32,474)
Income (loss) from discontinued operations, net of tax	3	(25)		(54)	592	(98)	98	(237)
Net income including noncontrolling interests	5,935	11,612	8,314	2,695	5,145	5,325	4,047	(2,668)	28,556	11,849	(36,492)
Less: Net income attributable to noncontrolling interests	339	233	552	163	794	(348)	(421)	(1,639)	1,287	(1,614)	338
Net income attributable to Comfort Systems USA, Inc.	5,596	11,379	7,762	2,532	4,351	5,673	4,468	(1,029)	27,269	13,463	(36,830)
Basic-
Income from continuing operations (in dollars per share)	$ 0.15	$ 0.31	$ 0.21	$ 0.07	$ 0.10	$ 0.15	$ 0.12	$ (0.02)	$ 0.73	$ 0.35	$ (0.88)
Income from discontinued operations (in dollars per share)					$ 0.02			$ (0.01)		$ 0.01	$ (0.11)
Net income (loss) (in dollars per share)	$ 0.15	$ 0.31	$ 0.21	$ 0.07	$ 0.12	$ 0.15	$ 0.12	$ (0.03)	$ 0.73	$ 0.36	$ (0.99)
Diluted-
Income from continuing operations (in dollars per share)	$ 0.15	$ 0.30	$ 0.21	$ 0.07	$ 0.10	$ 0.15	$ 0.12	$ (0.02)	$ 0.73	$ 0.35	$ (0.88)
Income from discontinued operations (in dollars per share)					$ 0.02			$ (0.01)		$ 0.01	$ (0.11)
Net income (loss) (in dollars per share)	$ 0.15	$ 0.30	$ 0.21	$ 0.07	$ 0.12	$ 0.15	$ 0.12	$ (0.03)	$ 0.73	$ 0.36	$ (0.99)
Net cash provided by (used in) operating activities	14,641	27,433	6,700	(10,351)	27,078	16,455	6,793	(19,816)	38,423	30,510	29,680
Quarterly Results of Operations (Unaudited)
Net income after-tax	5,596	11,379	7,762	2,532	4,351	5,673	4,468	(1,029)	27,269	13,463	(36,830)
Net diluted income after-tax (in dollars per share)	$ 0.15	$ 0.30	$ 0.21	$ 0.07	$ 0.12	$ 0.15	$ 0.12	$ (0.03)	$ 0.73	$ 0.36	$ (0.99)
Adjustments
Quarterly Results of Operations (Unaudited)
Revenue									3,300
Net income attributable to Comfort Systems USA, Inc.									1,300
Diluted-
Net income (loss) (in dollars per share)									$ 0.03
Quarterly Results of Operations (Unaudited)
Net income after-tax									$ 1,300
Net diluted income after-tax (in dollars per share)									$ 0.03