Capital Stock (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
Aug. 31, 2024	Aug. 31, 2021	Sep. 30, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Capital Stock
Common shares as presented in the accompanying Consolidated Balance Sheets			30,809,483	30,809,483	30,781,699
Common shares in treasury			5,056,771	5,056,771	4,995,414
Board of Directors authorized an expanded stock repurchase program	$ 200.0		$ 200.0	$ 200.0
Stock repurchases during period, shares			0	80,500	140,000	257,500
Stock repurchased during period, value				$ 8.0	$ 12.4	$ 20.0
Share Repurchase Program, Period in Force	3 years	3 years

Amount authorized for purchase of share under share repurchase plan. Includes, but is not limited to, repurchase of stock and unit of ownership.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Period share may be purchased under authorized share repurchase plan, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, repurchase of stock and unit of ownership.

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Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern 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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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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Number of previously issued common shares repurchased by the issuing entity and held in treasury.

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