Basis of Presentation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2016	Sep. 30, 2016	Sep. 30, 2015
Entity Information [Line Items]
Cash and cash equivalents, Carrying value	$ 512.4	$ 906.8	$ 906.8	$ 1,303.2	$ 1,383.8
Business Acquisition, Share Price	$ 17.75
Payments to Acquire Businesses and Interest in Affiliates	$ 560.0
Business Acquisition, Percentage of Voting Interests Acquired	75.00%
Subsidiaries [Member]
Entity Information [Line Items]
Cash and cash equivalents, Carrying value	$ 40.8			$ 40.5
Other Segments [Member]
Entity Information [Line Items]
General and administrative expense		1.1	3.6
Other income		$ 1.9	$ 5.6