Revenue Recognition - Dual Reporting - Consolidated Statement of Shareowners' Equity (Details) - USD ($) $ in Millions		3 Months Ended
	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings, beginning balance		$ 1,274.3	$ 2,156.2	$ 1,617.5
Net income (loss)		80.3	(236.4)
Other comprehensive income (loss)		(35.0)	3.5
Balances without adoption of ASC 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net income (loss)		82.6
Retained earnings
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings, beginning balance	$ 6,204.2	6,167.6	5,759.7	6,198.1	$ 6,103.4
Net income (loss)	80.3	80.3	(236.4)
Retained earnings | Balances without adoption of ASC 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings, beginning balance				6,198.1
Net income (loss)		82.6
Accumulated other comprehensive loss
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings, beginning balance		(976.9)	(1,175.7)	$ (941.9)	$ (1,179.2)
Other comprehensive income (loss)	(35.0)	(35.0)	$ 3.5
Accumulated other comprehensive loss | Balances without adoption of ASC 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Other comprehensive income (loss)		(34.8)
Accounting Standards Update 2014-09 | Impact of Adoption
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net income (loss)		$ 2.3
Accounting Standards Update 2014-09 | Retained earnings | Impact of Adoption
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings, beginning balance	(6.1)
Net income (loss)	2.3
Accounting Standards Update 2014-09 | Accumulated other comprehensive loss | Impact of Adoption
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Other comprehensive income (loss)	$ 0.2