EQUITY-BASED INCENTIVE AWARDS: (Details 2) - USD ($)	1 Months Ended		3 Months Ended	12 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Dec. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Restricted Stock Units
Restricted stock units
Award outstanding at the end of the period (in shares)			32,900	32,900	32,900	29,977	32,900
Direct cost to the recipients of the restricted stock units				$ 0
Period over which unamortized compensation expense is expected to be amortized				18 months
Tax benefit related to compensation expense				$ 500,000	$ 500,000
Total intrinsic value of equity-based compensation awards vested						$ 1,300,000	$ 1,200,000
All Equity-Based Awards (stock options and restricted stock units)
Compensation expense related to the amortization of all equity - based compensation awards				$ 1,200,000	$ 1,300,000
Total unamortized compensation expense						$ 1,200,000
Number of Shares
Nonvested restricted stock units at the beginning of the period (in shares)			32,900	32,900
Granted (in shares)				13,000
Vested (in shares)				(15,923)
Nonvested restricted stock units at the end of the period (in shares)				29,977	32,900
Weighted Average Fair Value
Nonvested restricted stock units at the beginning of the period (in dollars per share)			$ 84.75	$ 84.75
Granted (in dollars per share)				83.30
Vested (in dollars per share)				82.93
Nonvested restricted stock units at the end of the period (in dollars per share)				$ 80.00	$ 84.75
Restricted Stock Units 1
Restricted stock units
Service period		36 months
Estimated fair value of award at grant date		$ 935,000
Award outstanding at the end of the period (in shares)				5,000		5,000
Fair value of non-vested awards at the end of the period						$ 400,000
Vested as of the balance sheet date (in shares)						10,000
Number of Shares
Granted (in shares)		15,000
Nonvested restricted stock units at the end of the period (in shares)				5,000
Restricted Stock Units 2
Restricted stock units
Estimated fair value of award at grant date	$ 1,486,000
Award outstanding at the end of the period (in shares)				11,977		11,977
Fair value of non-vested awards at the end of the period						$ 958,000
Number of Shares
Granted (in shares)	17,600
Nonvested restricted stock units at the end of the period (in shares)				11,977
Restricted Stock Units 2 | Vesting of awards equally in three anniversaries from the date of grant
Restricted stock units
Award outstanding at the end of the period (in shares)				9,337		9,337
Vested as of the balance sheet date (in shares)						5,623
Number of Shares
Nonvested restricted stock units at the end of the period (in shares)				9,337
Restricted Stock Units 2 | Vesting of awards equally in five anniversaries from the date of grant
Restricted stock units
Award outstanding at the end of the period (in shares)				2,640		2,640
Number of Shares
Nonvested restricted stock units at the end of the period (in shares)				2,640
Restricted Stock Units 3
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)				13,000		13,000
Fair value of non-vested awards at the end of the period						$ 1,040,000
Number of Shares
Granted (in shares)			13,000
Nonvested restricted stock units at the end of the period (in shares)				13,000
Restricted Stock Units 3 | Vesting of awards equally in three anniversaries from the date of grant
Restricted stock units
Award outstanding at the end of the period (in shares)				13,000		13,000
Number of Shares
Nonvested restricted stock units at the end of the period (in shares)				13,000
Minimum | Restricted Stock Units 2
Restricted stock units
Service period	36 months
Maximum | Restricted Stock Units 2
Restricted stock units
Service period	60 months