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Revenue Recognition - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended
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Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2023
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |  |  |
Passed through costs included in revenue and cost of sales | $ 8,600.0 | $ 8,900.0 | $ 7,700.0
Transaction price, allocated | 19,700.0 |  |
Contract liabilities, revenue recognized | 918.9 | 801.0 |
Significant claims recorded in contract assets and other non-current assets | 400.0 | 180.0 |
Trade receivables sold with no financial and legal obligations | $ 268.2 | $ 319.5 |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-10-01 |  |  |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |  |  |
Revenue, remaining performance obligation (as percent) | 57.00% |  |
Revenue, performance obligation expected timing of satisfaction period | 12 months |  |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-10-01 |  |  |
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |  |  |
Revenue, performance obligation expected timing of satisfaction period | 2 years |  |

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- Definition The amounts in excess of the agreed contract price (or amounts not included in the original contract price) that the company seeks to collect from customers or others for delays, errors in specifications and designs, contract terminations, change orders in dispute or unapproved as to both scope and price or other causes of unanticipated additional costs recorded in contract assets and other non current assets. + References No definition available. + Details
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- Definition The costs of subcontracts for services and other direct costs incurred by the entity on behalf of its clients. These costs are passed through to clients and included in revenue and cost of revenue. + References No definition available. + Details
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- Definition The amount of trade receivables sold, which the entity does not retain financial and legal obligations, at reporting date. + References No definition available. + Details
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- Definition Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 606 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 8 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479806/606-10-50-8 + Details
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- Definition Amount of transaction price allocated to performance obligation that has not been recognized as revenue. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (a) -SubTopic 10 -Topic 606 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479806/606-10-50-13 + Details
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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. + Details
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- Definition Period in which remaining performance obligation is expected to be recognized as revenue, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (b)(1) -SubTopic 10 -Topic 606 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479806/606-10-50-13 + Details
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- Definition Percentage of remaining performance obligation to total remaining performance obligation not recognized as revenue. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (b)(1) -SubTopic 10 -Topic 606 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479806/606-10-50-13 + Details
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