Income Taxes - Net Deferred Income Tax Liability (Details) - USD ($) $ in Millions	Sep. 30, 2016	Sep. 30, 2015
Income Tax Examination [Line Items]
Other noncurrent assets	$ 24.4	$ 30.2
Deferred tax liabilities	42.8	39.9
Net Deferred Income Tax Liability	32.0	32.1
Other noncurrent assets
Income Tax Examination [Line Items]
Other noncurrent assets	10.7	7.8
Deferred tax liabilities
Income Tax Examination [Line Items]
Deferred tax liabilities	$ 42.7	$ 39.9