Commitments and Contingencies - Other and Bonds (Details) - Surety	12 Months Ended
Dec. 31, 2019
Minimum
Surety
Percentage of business which has required bonds	15.00%
Maximum
Surety
Percentage of business which has required bonds	25.00%

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