Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Income tax expense (benefit), including discontinued operations	$ 1.0	$ (4.5)	$ 109.0	$ (7.1)
Tax credit		$ 1.3	$ 2.3
Corporate Tax Rate per The Tax Cuts and Jobs Acts (TTCJA) [Line Items]
Provisional tax expense per the Tax Cuts Cuts and Jobs Act	$ 112.6
Maximum
Corporate Tax Rate per The Tax Cuts and Jobs Acts (TTCJA) [Line Items]
Corporate Tax Rate per The Tax Cuts and Jobs Acts (TTCJA)	35.00%		35.00%
Minimum
Corporate Tax Rate per The Tax Cuts and Jobs Acts (TTCJA) [Line Items]
Corporate Tax Rate per The Tax Cuts and Jobs Acts (TTCJA)	21.00%		21.00%