Commitments and Contingencies - Narrative (Details) - USD ($)	3 Months Ended			12 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2023
Guarantor Obligations [Line Items]
Additional bonding capacity	$ 556,600,000			$ 556,600,000
Cash collateral requirement for guarantees				2 years
Probable liquidated damages				$ 2,700,000
Loss contingency, estimate of actual or projected loss	3,900,000			3,900,000
Failure to meet contractual commitments, reduction to revenue	1,000,000.0	$ 1,700,000	$ 1,600,000	700,000
Facility Agreement | Powell (UK) Limited
Guarantor Obligations [Line Items]
Guarantee liability, letters of credit	7,600,000			7,600,000
Revolving credit facility	9,800,000			9,800,000
Amount of credit facility remaining borrowing capacity	2,200,000			2,200,000
Surety Bond
Guarantor Obligations [Line Items]
Guarantee liability, letters of credit	$ 393,400,000			$ 393,400,000