Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
U.S. federal statutory tax rate (percent)	21.00%			35.00%
Discrete net tax expense related to Tax Act	$ 3.2				$ 43.8
Reversal of non-recurring benefit related to U.S. taxation of deemed foreign dividends					56.2
Tax benefit related to finalization of assessment of impacts of Tax Act					$ 12.4
Discrete net tax expense based on provisional estimates related to Tax Act						$ 206.5
Impact of new tax law on equity affiliate expense						$ 32.5
Deferred foreign income tax expense (benefit)			$ 38.8
Tax benefit related to settlement and release of reserves		$ 9.1
Effective tax rate (percent)	17.90%	19.40%			21.30%	30.60%
Income tax payments, net of refunds					$ 250.8	$ 319.1