Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income tax expense	$ 128.8	$ 112.4	$ 317.8	$ 272.8
Effective tax rate (percent)	34.00%	33.70%	34.50%	34.80%
Deferred tax assets net of DTL	$ 514.3		$ 514.3		$ 568.2
Valuation allowance for deferred income taxes	$ 9.2		$ 9.2		$ 10.1