Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Balance Type:	debit
Period Type:	duration

Basis of Presentation and Summary of Significant Accounting Policies - Share Repurchase Program (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Mar. 31, 2022	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Authorized amount repurchase of common stock					$ 50.0
Share repurchases			$ 3.3	$ 34.6
Completed common stock repurchase (in shares)	0	0
Remaining authorized repurchase amount	$ 12.0