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PA Consulting Redeemable Noncontrolling Interests - Narrative (Details) $ / shares in Units, $ in Thousands, £ in Millions |  |  | 3 Months Ended | 6 Months Ended | 53 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Mar. 20, 2026 USD ($) | Jan. 02, 2026 GBP (£) shares | Mar. 27, 2026 USD ($) $ / shares shares | Mar. 28, 2025 USD ($) | Mar. 27, 2026 USD ($) $ / shares shares | Mar. 28, 2025 USD ($) $ / shares | Jul. 31, 2025 | Jan. 02, 2026 $ / shares shares | Sep. 26, 2025 USD ($) $ / shares shares | Sep. 27, 2024 $ / shares
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |
Common stock, par value (in dollars per share) | $ / shares |  |  | $ 1 |  | $ 1 |  |  |  | $ 1 | $ 1.00
Common stock, issued (in shares) | shares |  |  | 118,190,953 |  | 118,190,953 |  |  |  | 119,081,294 |
Redemption of redeemable noncontrolling interests relating to the PA Consulting Transaction |  |  | $ (36,011) |  | $ (36,011) |  |  |  |  |
Redemption of redeemable noncontrolling interests relating to the PA Consulting Transaction |  |  |  |  | $ (883,623) | $ (4,066) |  |  |  |
Preference share effect on basic earnings per share (in dollars per share) | $ / shares |  |  |  |  | $ 0.11 | $ 0.05 |  |  |  |
Allocated share-based compensation expense |  |  |  | $ 8,000 |  | $ 13,900 |  |  |  |
Equity-Based Incentive Grants |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |
Accrued cumulative expense associated with the vested grants |  |  |  |  |  |  |  |  | $ 103,800 |
Allocated share-based compensation expense |  |  | 214,900 |  | $ 237,500 | 13,900 |  |  |  |
Equity-Based Incentive Grants | Share-Based Payment Arrangement, Tranche One |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |
Award vesting percentage |  |  |  |  |  |  | 40.00% |  |  |
Equity-Based Incentive Grants | Share-Based Payment Arrangement, Tranche Two |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |
Award vesting percentage | 60.00% |  |  |  |  |  |  |  |  |
PA Consulting |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |
Redemption of redeemable noncontrolling interests relating to the PA Consulting Transaction |  |  |  |  | (400) | $ (4,100) |  |  |  |
PA Consulting Employees |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |
Redemption of redeemable noncontrolling interests relating to the PA Consulting Transaction |  |  |  |  | (1,119,417) |  |  |  |  |
Ownership interest of employees (as a percent) |  |  |  |  |  |  |  |  | 71.00% |
Retained Earnings |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |
Redemption of redeemable noncontrolling interests relating to the PA Consulting Transaction |  |  | $ (36,011) |  | (36,011) |  |  |  |  |
PA Consulting Group Limited |  |  |  |  |  |  |  |  |  |
Business Combination [Line Items] |  |  |  |  |  |  |  |  |  |
Consideration transferred | £ |  | £ 1,210.0 |  |  |  |  |  |  |  |
Consideration paid in cash |  | £ 997.6 |  |  | $ 123,900 |  |  |  |  |
Business combination share issued (in shares) | shares |  | 2,043,537 |  |  |  |  |  |  |  |
Common stock, par value (in dollars per share) | $ / shares |  |  |  |  |  |  |  | $ 1.00 |  |
Business combination, additional consideration deferred, estimated equity value | £ |  | £ 75.0 |  |  |  |  |  |  |  |
Common stock, issued (in shares) | shares |  |  | 2,043,537 |  | 2,043,537 |  |  | 2,043,537 |  |
Initial consideration distributed in cash | $ 113,500 |  |  |  |  |  |  |  |  |
Business combination, additional deferred consideration payable to acquiree employees |  |  | $ 10,400 |  | $ 10,400 |  |  |  |  |
Cash in employee benefit trust |  |  | $ 116,500 |  | $ 116,500 |  |  |  | $ 1,400 |

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