Restructuring and Other Charges - Schedule of Restructuring and Other Charges Impacts on Reportable Segment Income by Line of Business (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 26, 2026	Jun. 27, 2025	Jun. 26, 2026	Jun. 27, 2025
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 21,395	$ 22,254	$ 39,565	$ 47,657
Professional Services and Employee Seperation
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	7,600	22,000	17,500	47,100
PA Consulting Group Limited
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	13,800		22,000
PA Consulting Group Limited \| Professional Services and Dedicated Internal Personnel
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	13,800		22,000
Operating Segments \| Infrastructure & Advanced Facilities
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	7,627	22,254	17,518	47,398
Operating Segments \| PA Consulting
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 13,768	$ 0	$ 22,047	$ 259

- Definition

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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- 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.

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