Business Segment Information (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Operating income (loss)	$ 516.5	$ 455.4	$ 971.5	$ 916.1
Contracts accounted for under percentage of completion
Segment Reporting Information [Line Items]
Operating income (loss)			$ 10.0	$ 10.0

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.

No definition available.

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