Revenue Recognition - Dual Reporting - Consolidated Statement of Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net income (loss)	$ 80.3	$ (236.4)
Currency translation adjustments	(28.5)	$ (16.1)
Impact of Adoption | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net income (loss)	2.3
Currency translation adjustments	0.2
Balances without adoption of ASC 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net income (loss)	82.6
Currency translation adjustments	$ (28.3)