Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Effective income tax rate	22.60%	25.50%	22.10%	25.50%
U.S. statutory rate	35.00%	35.00%	35.00%	35.00%
Gross unrecognized tax benefits	$ 48.7		$ 48.7		$ 43.9
Accrued interest and penalties related to unrecognized tax benefits	4.8		4.8		$ 5.1
Net reduction of income tax provision related to unrecognized tax benefits, tax penalties, accrued interest and offsetting tax assets	31.7		31.7
Reasonably possible amount of reduction in gross unrecognized tax benefits for the next twelve months	31.4		31.4
Reasonably possible amount of net reduction to income tax provision if unrecognized tax benefits were recognized	$ 15.2		$ 15.2
Earliest open year for income tax examinations, U.S. federal			2012
Earliest open tax year for income tax examinations, state, local and non-U.S.			2003