Revenue from Contracts with Customers - Narratives (Details)	3 Months Ended
Mar. 31, 2025	Mar. 31, 2024
Revenue from Contracts with Customers
Percentage impact on revenue from performance obligations satisfied in previous period	5.80%	4.10%

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