Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income tax expense	$ 83.6	$ 78.2
Effective tax rate (percent)	34.60%	35.40%
Deferred tax assets net of DTL	$ 552.3		$ 568.2
Valuation allowance for deferred income taxes	$ 10.1		$ 10.1