Commitments and Contingencies - Bonds (Details) - Surety	3 Months Ended
Mar. 31, 2018
Minimum
Surety
Percentage of business which has required bonds	20.00%
Maximum
Surety
Percentage of business which has required bonds	30.00%

Represents the percentage of business which has required bonds.

No definition available.

Name:	fix_PercentageOfBusinessWhichHasRequiredBonds
Namespace Prefix:	fix_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration