EQUITY-BASED INCENTIVE AWARDS - Omnibus Plans and Stock Options (Details) $ / shares in Units, $ in Millions	12 Months Ended
Sep. 30, 2020 USD ($) item $ / shares shares	Sep. 30, 2019 USD ($) $ / shares shares
EQUITY-BASED INCENTIVE AWARD
Number of incentive plans \| item	2
Stock options issued and outstanding
Number Outstanding (in shares) \| shares	34,350
Weighted-Average Exercise Price (in dollars per share) \| $ / shares	$ 80.33
Omnibus Plans
EQUITY-BASED INCENTIVE AWARD
Number of shares of the company's common stock permitted for issuance under the plan \| shares	135,000
Number of shares awarded pursuant to the plan \| shares	101,280
Number of additional shares that may be awarded under the plan \| shares	33,720
Stock Options
EQUITY-BASED INCENTIVE AWARD
Awards issued (in shares) \| shares	0	5,450
Vesting period	5 years	5 years
Estimated fair value of the stock option awards using the Black-Scholes option pricing model \| $		$ 0.2
Stock Option Pricing Assumptions
Risk-free interest rate (as a percent)		2.55%
Dividend yield (as a percent)		0.80%
Expected volatility (as a percent)		45.10%
Expected life		6 years
Stock options issued and outstanding
Expiration period	10 years	10 years
Number Outstanding (in shares) \| shares	34,350	36,450
Weighted-Average Exercise Price (in dollars per share) \| $ / shares	$ 80.33	$ 78.67
Number Exercisable (in shares) \| shares	22,890
Exercisable, Weighted-Average Exercise Price (in dollars per share) \| $ / shares	$ 72.67
Number of Shares
Granted (in shares) \| shares	0	5,450
Exercised (in shares) \| shares	(2,100)
Weighted Average Exercise Price
Exercised (in dollars per share) \| $ / shares	$ 51.50
Aggregate intrinsic value and fair value of options outstanding
Compensation expense \| $	$ 0.1	$ 0.1
Total unamortized compensation expense \| $	$ 0.2
Amortization period of unamortized compensation expense	29 months
Aggregate intrinsic value of options outstanding \| $		0.2
Aggregate intrinsic value of options exercisable \| $		0.2
Total fair value of options vested \| $	$ 0.4	0.4
Stock Options \| Maximum
Aggregate intrinsic value and fair value of options outstanding
Aggregate intrinsic value of options outstanding \| $	0.1
Aggregate intrinsic value of options exercisable \| $	0.1
Total intrinsic value of options exercised \| $	$ 0.1	$ 0.1

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Represents the grant-date fair value of options granted during the reporting period as calculated by applying the Black-Scholes option pricing methodology.

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Number of share instruments newly issued at the reporting date under a share-based compensation plan, net of forfeitures.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cost to be recognized for option under share-based payment arrangement.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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Number of shares authorized for issuance under share-based payment arrangement.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Net number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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Number of share options (or share units) exercised during the current period.

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