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Technology Platform And Personnel And Corporate Overhead Cost

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Amount of expense for salary, wage, profit sharing; incentive and equity-based compensation; and other employee benefit. Other employee benefit expense includes, but is not limited to, service component of net periodic benefit cost for defined benefit plan. Excludes compensation cost in cost of good and service sold.

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Amount of increase in the fair value of derivatives recognized in the income statement.

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Amount of gain (loss) on termination of lease before expiration of lease term.

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The charge against earnings in the period to reduce the carrying amount of real property to fair value.

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Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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The amount of the additional liability or refund received or expected based on a final settlement with a taxing authority.

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The net result for the period of deducting operating expenses from operating revenues.

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Carrying amount as of the balance sheet date of known and reasonably estimable amounts of recoveries from third-parties pertaining to an entity's environmental remediation obligations. An entity's balance sheet may include several assets that relate to an environmental remediation obligation. Among them are the following: a. Receivables from other potentially responsible parties that are not providing initial funding; b. anticipated recoveries from insurers; and c. anticipated recoveries from prior owners as a result of indemnification agreements.

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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Segment Information - Schedule of Total Revenues, Segment Operating Profit and Total Asset for Reporting Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 27, 2024	Jun. 28, 2024	Mar. 29, 2024	Dec. 29, 2023	Sep. 29, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 30, 2022	Sep. 27, 2024	Sep. 29, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Total Segment Operating Profit	$ 196,205	$ 170,987	$ 183,244	$ 142,000	$ 168,358	$ 167,688	$ 185,847	$ 154,591	$ 692,436	$ 676,484	$ 539,884
Restructuring, Transaction and Other Charges	(43,400)	(57,000)	(37,300)	(41,300)	(47,900)	(13,200)			(179,090)	(145,911)	(192,477)
Total Other (Expense) Income, net									84,850	(155,509)	(62,387)
Earnings from Continuing Operations Before Taxes	393,606	$ 136,466	$ 144,009	$ 103,205	132,091	$ 125,207	148,670	115,007	777,286	520,975	477,497
Amortization of intangible assets									152,667
Restructuring charges									134,862
Recognized impairment charges					$ 8,700		$ 10,100	$ 27,100		46,700
Recorded third-party environmental recoveries receivable											27,000
Gain on termination of lease											8,700
Amentum Holdings, Inc. \| Discontinued Operations, Spinoff \| SpinCo Business
Segment Reporting Information [Line Items]
Equity method investment retained after disposal, mark-to market gains	186,900								186,900
Interest Rate Swap
Segment Reporting Information [Line Items]
Derivative, gain on derivative	$ 35,200								35,200
JKC Australia L N G Pty Limited \| Settled Litigation
Segment Reporting Information [Line Items]
Pre-tax settlement less insurance recoveries											91,300
Operating Segments
Segment Reporting Information [Line Items]
Total Segment Operating Profit									871,526	822,395	732,361
Operating Segments \| Employee Separation Costs
Segment Reporting Information [Line Items]
Restructuring charges									6,400	14,300
Operating Segments \| Professional Services and Employee Separation Costs
Segment Reporting Information [Line Items]
Restructuring charges									163,400	61,100
Other Corporate Expenses \| Other Expense
Segment Reporting Information [Line Items]
Amortization of intangible assets									152,700	147,200	149,800
Compensation expense, cost reductions										15,000
Compensation expense, employee benefit program costs										41,000
Technology platform and personnel and corporate overhead costs										26,000
Infrastructure & Advanced Facilities \| Operating Segments
Segment Reporting Information [Line Items]
Total Segment Operating Profit									632,276	585,392	500,136
PA Consulting \| Operating Segments
Segment Reporting Information [Line Items]
Total Segment Operating Profit									$ 239,250	$ 237,003	$ 232,225