Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014	Sep. 30, 2014
Income Tax Disclosure [Abstract]
Effective income tax rate	25.50%	27.40%	25.50%	27.40%
U.S. statutory rate	35.00%	35.00%	35.00%	35.00%
Gross unrecognized tax benefits	$ 40.5		$ 40.5		$ 38.9
Accrued interest and penalties related to unrecognized tax benefits	5.6		5.6		8.1
Net reduction of income tax provision related to unrecognized tax benefits, tax penalties, accrued interest and offsetting tax assets	22.3		22.3
Reasonably possible amount of decrease in gross unrecognized tax benefits for the next twelve months	20.5		20.5
Reasonably possible amount of net reduction to income tax provision if unrecognized tax benefits were recognized	$ 3.1		$ 3.1
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