New Accounting Guidance (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019
New Accounting Pronouncements [Line Items]
Equity	$ 13,491.6	$ 13,134.8	$ 12,443.1	$ 12,023.4	$ 11,723.7	$ 11,388.3
Retained Earnings
New Accounting Pronouncements [Line Items]
Equity	$ 15,400.2	$ 15,200.0	14,875.7	$ 14,686.6	$ 14,537.2	$ 14,138.4
Cumulative-effect adjustment | Retained Earnings
New Accounting Pronouncements [Line Items]
Equity			$ 1.3