CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CONSOLIDATED STATEMENTS OF OPERATIONS
REVENUE	$ 1,787,922	$ 1,634,340	$ 1,580,519
COST OF SERVICES	1,421,641	1,290,331	1,262,390
Gross profit	366,281	344,009	318,129
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES	266,586	243,201	228,965
GOODWILL IMPAIRMENT	1,105
GAIN ON SALE OF ASSETS	(670)	(761)	(880)
Operating income	99,260	101,569	90,044
OTHER INCOME (EXPENSE):
Interest income	70	9	72
Interest expense	(3,156)	(2,345)	(1,753)
Changes in the fair value of contingent earn-out obligations	3,715	731	225
Other	1,049	1,097	76
Other income (expense)	1,678	(508)	(1,380)
INCOME BEFORE INCOME TAXES	100,938	101,061	88,664
PROVISION FOR INCOME TAXES	45,666	36,165	31,224
NET INCOME INCLUDING NONCONTROLLING INTERESTS	55,272	64,896	57,440
Less: Net income attributable to noncontrolling interests			8,076
NET INCOME ATTRIBUTABLE TO COMFORT SYSTEMS USA, INC.	$ 55,272	$ 64,896	$ 49,364
INCOME PER SHARE ATTRIBUTABLE TO COMFORT SYSTEMS USA, INC.:
Basic (in shares)	$ 1.48	$ 1.74	$ 1.32
Diluted (in shares)	$ 1.47	$ 1.72	$ 1.30
SHARES USED IN COMPUTING INCOME PER SHARE:
Basic (in shares)	37,239	37,335	37,442
Diluted (in shares)	37,672	37,811	37,868
DIVIDENDS PER SHARE (in dollars per share)	$ 0.295	$ 0.275	$ 0.250