Commitments and Contingencies (Details) $ in Millions	9 Months Ended
Jun. 30, 2026 USD ($)
Guarantee Obligations [Line Items]
Additional bonding capacity	$ 707.6
Cash collateral required for guarantees, period (greater than)	2 years
Contracts with probable exposure to liquidated damages	$ 6.3
Probable exposure potential increase	9.3
Change in contract estimates, reduction to revenue	5.1
Surety Bonds
Guarantee Obligations [Line Items]
Guarantee liability	492.4
Facility Agreement \| Powell (UK) Limited
Guarantee Obligations [Line Items]
Guarantee liability	5.7
Revolving credit facility	19.9
Amount of credit facility remaining borrowing capacity	14.2
Revolving Credit Facility \| U.S. Revolver
Guarantee Obligations [Line Items]
Amount of credit facility remaining borrowing capacity	46.1
Revolving Credit Facility \| U.S. Revolver \| Financial Standby Letter of Credit
Guarantee Obligations [Line Items]
Guarantee liability	$ 103.9

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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