Commitments and Contingencies (Details)	9 Months Ended
Jun. 30, 2021 USD ($)
Guarantee Obligations [Line Items]
Additional bonding capacity	$ 458,800,000
Cash collateral required for guarantees, period (greater than)	2 years
Facility Agreement \| Powell (UK) Limited
Guarantee Obligations [Line Items]
Guarantee liability	$ 7,700,000
Revolving credit facility	9,700,000
Amount of credit facility remaining borrowing capacity	2,000,000.0
Surety Bonds
Guarantee Obligations [Line Items]
Guarantee liability	141,200,000
U.S. Revolver \| Amended and Restated Credit Agreement
Guarantee Obligations [Line Items]
Revolving credit facility	75,000,000.0
Amount of credit facility remaining borrowing capacity	35,100,000
U.S. Revolver \| Financial Standby Letter of Credit \| Amended and Restated Credit Agreement
Guarantee Obligations [Line Items]
Guarantee liability	$ 39,900,000

Cash Collateral Required for Guarantees, Period

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- Definition

Commitments and contingencies additional bonding capacity.

+ References

No definition available.

+ Details

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- Definition

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=124440162&loc=d3e12069-110248

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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