Revenue from Contracts with Customers - Narratives (Details)	3 Months Ended	9 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Revenue from Contracts with Customers
Percentage impact on revenue from performance obligations satisfied in previous period	1.70%	0.80%	2.70%	1.30%

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