Revenue from Contracts with Customers - Narratives (Details)	3 Months Ended	6 Months Ended
Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Revenue from Contract with Customer [Abstract]
Percentage impact on revenue from performance obligations satisfied in previous period	4.40%	2.40%	5.00%	3.20%

Percentage of revenue attributable to performance obligation satisfied or partially satisfied in previous reporting periods. Includes, but is not limited to, change in transaction price.

No definition available.

Name:	fix_ContractWithCustomerPerformanceObligationSatisfiedInPreviousPeriodPercentage
Namespace Prefix:	fix_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration