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Debt - URS Senior Notes (Details) - USD ($) $ in Thousands		12 Months Ended
	Aug. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019	Oct. 17, 2014
Debt
Repayments of debt		$ 797,252	$ 248,522
Proceeds from secured delayed draw term loan facility		3,638,916	4,452,078	$ 7,700,774
Prepayment premium on redemption of unsecured senior notes		$ 117,500	$ 16,986
URS Senior Notes
Debt
Prepayment premium on redemption of unsecured senior notes	$ 17,000
URS Senior Notes | 2022 URS Senior Notes
Debt
Interest rate (as a percent)					5.00%
Redemption price (as percent of principal)	106.835%
Repayments of debt	$ 248,500
Proceeds from secured delayed draw term loan facility	$ 248,500

X

- Definition

Represents the prepayment premium on redemption of unsecured notes for financing activities.

+ References

No definition available.

+ Details

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X

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ 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 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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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

No definition available.

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- Definition

Percentage of principal amount of debt redeemed.

+ References

No definition available.

+ Details

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- Definition

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3255-108585

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- Definition

The cash outflow to repay long-term debt that is not secured by collateral. Excludes repayments of tax exempt unsecured debt.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3291-108585

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