Business Segment Information (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Operating income (loss)	$ 569.7	$ 515.8	$ 1,541.2	$ 1,431.9
Contracts accounted for under percentage of completion
Segment Reporting Information [Line Items]
Operating income (loss)			$ 15.0	$ 25.0