Earnings per Share (Schedule of Weighted-Average Shares Outstanding) (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Schedule Of Weighted Average Number Of Shares [Line Items]
Basic weighted-average shares outstanding (in shares)	54.0	57.2	54.5	57.4
Effect of dilutive securities (in shares)	0.1	0.3	0.1	0.3
Diluted weighted-average shares outstanding (in shares)	54.1	57.5	54.6	57.7
RSE awards
Schedule Of Weighted Average Number Of Shares [Line Items]
Effect of dilutive securities (in shares)	0.1	0.3	0.1	0.3