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	35.70%	24.60%	34.20%	27.60%
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance		13.00%		7.00%
Effective Income Tax Reconciliation Reinstatement of Research and Development Credits			1.60%
Gross unrecognized tax benefits, excluding income tax penalties and interest	$ 41.4		$ 41.4		$ 32.8
Net unrecognized tax benefits, excluding interest and penalties that would affect the Company's net income if recognized	23.7		23.7
Interest and penalties			1.5	1.7
Accruals for payment of interest and penalties	19.0		19.0
Estimated reduction in unrecognized tax benefits due to tax audit resolutions during the next twelve months	$ 15.5		$ 15.5
Income Tax Expense (Benefit), Discrete Items, Percentage of Pre-Tax Income	0.50%	11.20%	0.80%	7.10%
Effective Income Tax Rate Reconciliation, Tax Settlement, State and Local, Percent		(1.80%)		(1.00%)
Other Discrete Items, Percentage of Pre-Tax Income			(0.80%)	1.00%