EQUITY-BASED INCENTIVE AWARDS - Stock Options (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2017 USD ($) item $ / shares shares	Sep. 30, 2016 USD ($) $ / shares shares
Omnibus plan and stock option activity
Number of incentive plans | item	2
Number of shares of the company's common stock permitted for issuance under the plan | shares	225,000
Number of shares awarded pursuant to the plan | shares	190,935
Number of additional shares that may be awarded under the plan | shares	34,065
Stock Options
Omnibus plan and stock option activity
Vesting period	5 years	5 years
Estimated fair value of the stock option awards using the Black-Scholes option pricing model | $	$ 0.1	$ 0.1
Expiration period	10 years	10 years
Stock Option Pricing Assumptions
Risk-free interest rate (as a percent)	2.12%	1.98%
Dividend yield (as a percent)	0.60%	0.90%
Expected volatility (as a percent)	22.40%	24.30%
Expected life	6 years	6 years
Stock options issued and outstanding
Number Outstanding (in shares) | shares	28,300	22,800
Weighted-Average Exercise Price (in dollars per share) | $ / shares	$ 74.75	$ 69.79
Number Exercisable (in shares) | shares	13,200
Exercisable, Weighted-Average Exercise Price (in dollars per share) | $ / shares	$ 63.33
Number of Shares
Granted (in shares) | shares	6,000	5,500
Exercised (in shares) | shares	(500)
Weighted Average Exercise Price
Granted (in dollars per share) | $ / shares	$ 91.65
Exercised (in dollars per share) | $ / shares	$ 51.50
Aggregate intrinsic value and fair value of options outstanding
Compensation expense related to the amortization of all equity - based compensation awards | $	$ 0.1	$ 0.1
Total unamortized compensation expense | $	$ 0.2
Amortization period of unamortized compensation expense	40 months
Aggregate intrinsic value of options outstanding | $	$ 0.5	0.5
Aggregate intrinsic value of options exercisable | $	0.4	0.3
Total intrinsic value of options | $	0.1	0.1
Total fair value of options vested | $	$ 0.4	$ 0.4