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		6 Months Ended
	Mar. 27, 2026	Mar. 28, 2025	Mar. 27, 2026	Mar. 28, 2025
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 14,171	$ 10,663	$ 18,169	$ 25,403
Professional Services and Employee Seperation
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	7,600	10,200	9,900	25,100
PA Consulting Group Limited
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	6,500		8,300
PA Consulting Group Limited \| Professional Services and Dedicated Internal Personnel
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	6,500		8,300
Operating Segments \| Infrastructure & Advanced Facilities
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	7,649	10,168	9,890	25,144
Operating Segments \| PA Consulting
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 6,522	$ 495	$ 8,279	$ 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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