Acquisitions and Divestitures Definite-lived intangible assets acquired (Details) - USD ($) $ in Millions	Mar. 31, 2019	Sep. 30, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	$ 1,215.8	$ 1,182.2
Finite-Lived Intangible Assets, Accumulated Amortization	502.5	371.0
Finite-Lived Intangible Assets, Net	713.3	811.2
Acquired and reacquired rights
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Gross	1,110.3	1,081.7
Finite-Lived Intangible Assets, Accumulated Amortization	444.7	320.1
Finite-Lived Intangible Assets, Net	$ 665.6	$ 761.6