Earnings per Share - Reconciliation of Average Common Shares Outstanding (Details) - shares shares in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Earnings Per Share [Abstract]
Basic average common shares outstanding (in shares)	70.7	72.4	70.4	72.3
Impact of restricted shares, restricted share units and performance share units (in shares)	0.7	1.0	0.9	1.0
Diluted average common shares outstanding (in shares)	71.4	73.4	71.3	73.3