Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2014	Sep. 30, 2014
Use of Estimates
Contract estimate writedown	$ 2.2	$ 4.4

The amount by which the estimate of total contract revenue is exceeded by the estimate of total contract costs.

No definition available.

Name:	fix_ProvisionsForLossOnContracts
Namespace Prefix:	fix_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration