Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Allowance for possible losses and sales returns - accounts receivable [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
BALANCE AT BEGINNING OF PERIOD	$ 26.8	$ 26.0	$ 31.4
CHARGED TO COSTS AND EXPENSES	4.3	2.1	1.8
CHARGED TO OTHER ACCOUNTS	2.0	2.2	0.1
DEDUCTIONS NET OF RECOVERIES	(8.0)	(3.5)	(7.3)
BALANCE AT END OF PERIOD	25.1	26.8	26.0
Valuation allowance against deferred tax assets [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
BALANCE AT BEGINNING OF PERIOD	26.9	40.7	28.3
CHARGED TO COSTS AND EXPENSES	30.8	(14.9)	4.0
CHARGED TO OTHER ACCOUNTS	0.0	0.0	11.1
DEDUCTIONS NET OF RECOVERIES	0.5	1.1	(2.7)
BALANCE AT END OF PERIOD	$ 58.2	$ 26.9	$ 40.7