Accounts Payable and Other Current Liabilities - Schedule of Other Payables and Current Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2018	Sep. 30, 2017
Other Liabilities Disclosure [Abstract]
Accrued expenses and other	$ 129.0	$ 125.8
Accrued interest	41.3	55.4
Income taxes payable	62.6	78.0
Accounts Payable and Accrued Liabilities, Current	$ 360.7	$ 373.1