Income Taxes - Current and Deferred Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Current Federal Tax Expense (Benefit)									$ (1.9)	$ 0.8	$ 0.7
Current State and Local Tax Expense (Benefit)									(0.8)	0.5	1.2
Current Foreign Tax Expense (Benefit)									24.9	22.4	16.7
Current Income Tax Expense (Benefit)									22.2	23.7	18.6
Deferred Income Tax Expense (Benefit)									3.7	22.3	(9.8)
Income tax expense	$ 6.9	$ 5.3	$ 7.5	$ 6.2	$ 4.8	$ 8.9	$ 6.8	$ 25.5	$ 25.9	$ 46.0	$ 8.8