Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Oct. 01, 2018	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	$ 2,513.5			$ 2,513.5
Total other comprehensive income (loss), net of tax		$ (10.9)	$ 17.3	(19.7)	$ 19.9
Balance at end of period	2,453.1	2,499.7		2,499.7
Employee Pension and Postretirement Benefits, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(10.9)	(20.0)	(45.7)	(10.9)	(46.2)
Other comprehensive income (loss) before reclassifications		(3.9)	0.0	(3.9)	0.0
Amounts reclassified from accumulated other comprehensive income (loss)		0.1	0.5	0.1	1.0
Total other comprehensive income (loss), net of tax		(3.8)	0.5	(3.8)	1.0
Balance at end of period	(20.0)	(23.8)	(45.2)	(23.8)	(45.2)
Cumulative Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(96.2)	(105.0)	(76.5)	(96.2)	(78.6)
Other comprehensive income (loss) before reclassifications		(6.9)	16.5	(15.7)	18.6
Amounts reclassified from accumulated other comprehensive income (loss)		0.0	0.0	0.0	0.0
Total other comprehensive income (loss), net of tax		(6.9)	16.5	(15.7)	18.6
Balance at end of period	(96.2)	(111.9)	(60.0)	(111.9)	(60.0)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	0.3	0.3	(0.2)	0.3	(0.2)
Other comprehensive income (loss) before reclassifications		(0.2)	0.3	(0.2)	0.3
Amounts reclassified from accumulated other comprehensive income (loss)		0.0	0.0	0.0	0.0
Total other comprehensive income (loss), net of tax		(0.2)	0.3	(0.2)	0.3
Balance at end of period	0.3	0.1	0.1	0.1	0.1
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(106.8)	(124.7)	(122.4)	(106.8)	(125.0)
Other comprehensive income (loss) before reclassifications		(11.0)	16.8	(19.8)	18.9
Amounts reclassified from accumulated other comprehensive income (loss)		0.1	0.5	0.1	1.0
Total other comprehensive income (loss), net of tax		(10.9)	17.3	(19.7)	19.9
Balance at end of period	(115.9)	$ (135.6)	$ (105.1)	$ (135.6)	$ (105.1)
Accounting Standards Update 2018-02 [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	0.0
Accounting Standards Update 2018-02 [Member] | Employee Pension and Postretirement Benefits, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	(9.1)
Accounting Standards Update 2018-02 [Member] | Cumulative Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	0.0
Accounting Standards Update 2018-02 [Member] | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	0.0
Accounting Standards Update 2018-02 [Member] | Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ (9.1)