EQUITY-BASED INCENTIVE AWARDS - Restricted Stock Units (Details) - USD ($)	1 Months Ended			12 Months Ended
	Oct. 31, 2015	Oct. 31, 2014	Oct. 31, 2013	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Restricted Stock Units
Restricted stock units
Award outstanding at the end of the period (in shares)	29,977			29,977	29,977	28,567	29,977
Direct cost to the recipients of the restricted stock units				$ 0
Compensation expense related to the amortization of all equity - based compensation awards				1,300,000	$ 1,200,000
Tax benefit related to compensation expense				$ 500,000	$ 500,000
Total intrinsic value of equity-based compensation awards vested						$ 1,300,000	$ 1,300,000
Total unamortized compensation expense						$ 1,300,000
Period over which unamortized compensation expense is expected to be amortized				17 months
Number of Shares
Nonvested restricted stock units at the beginning of the period (in shares)	29,977			29,977
Granted (in shares)				13,250
Vested (in shares)				(14,660)
Nonvested restricted stock units at the end of the period (in shares)				28,567	29,977
Weighted Average Fair Value
Nonvested restricted stock units at the beginning of the period (in dollars per share)	$ 80.00			$ 80.00
Granted (in dollars per share)				83.90
Vested (in dollars per share)				83.95
Nonvested restricted stock units at the end of the period (in dollars per share)				$ 90.96	$ 80.00
Vested (in shares)				14,660
Restricted Stock Units Awarded October 2013
Restricted stock units
Estimated fair value of award at grant date			$ 1,486,000
Award outstanding at the end of the period (in shares)				6,649		6,649
Fair value of non-vested awards at the end of the period						$ 605,000
Number of Shares
Granted (in shares)			17,600
Vested (in shares)				(10,951)
Nonvested restricted stock units at the end of the period (in shares)				6,649
Weighted Average Fair Value
Vested (in shares)				10,951
Units scheduled to vest						4,669
Restricted Stock Units Awarded October 2013 | Vesting of awards equally in three anniversaries from the date of grant
Weighted Average Fair Value
Units scheduled to vest						1,980
Restricted Stock Units Awarded October 2014
Restricted stock units
Service period		36 months
Estimated fair value of award at grant date		$ 1,083,000
Award outstanding at the end of the period (in shares)				8,668		8,668
Fair value of non-vested awards at the end of the period						$ 788,000
Number of Shares
Granted (in shares)		13,000
Vested (in shares)				(4,332)
Nonvested restricted stock units at the end of the period (in shares)				8,668
Weighted Average Fair Value
Vested (in shares)				4,332
Units scheduled to vest						8,668
Restricted Stock Units Awarded October 2015
Restricted stock units
Estimated fair value of award at grant date	$ 1,112,000
Award outstanding at the end of the period (in shares)				13,250		13,250
Fair value of non-vested awards at the end of the period						$ 1,205,000
Number of Shares
Granted (in shares)	13,250
Nonvested restricted stock units at the end of the period (in shares)				13,250
Restricted Stock Units Awarded October 2015 | Vesting of awards equally in three anniversaries from the date of grant
Weighted Average Fair Value
Units scheduled to vest						13,000
Restricted Stock Units Awarded October 2015 | Vesting of awards equally in five anniversaries from the date of grant
Weighted Average Fair Value
Units scheduled to vest						250
Minimum | Restricted Stock Units Awarded October 2013
Restricted stock units
Service period			36 months
Minimum | Restricted Stock Units Awarded October 2015
Restricted stock units
Service period	36 months
Maximum | Restricted Stock Units Awarded October 2013
Restricted stock units
Service period			60 months
Maximum | Restricted Stock Units Awarded October 2015
Restricted stock units
Service period	60 months