Supplemental Information (Changes in Estimates) (Details) - USD ($) $ in Millions	3 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Change in Accounting Estimate [Line Items]
Operating income (loss)	$ 666.9	$ 652.0
Contracts accounted for under percentage of completion
Change in Accounting Estimate [Line Items]
Operating income (loss)	$ (30.0)	$ (25.0)

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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