Revenue from Contracts with Customers - Narratives (Details)	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Revenue from Contracts with Customers
Percentage impact on revenue from performance obligations satisfied in previous period	2.30%	1.30%	1.10%

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