EQUITY-BASED INCENTIVE AWARDS - Restricted Stock Units (Details) - USD ($)	1 Months Ended				3 Months Ended
	Oct. 31, 2016	Oct. 31, 2015	Oct. 31, 2014	Oct. 31, 2013	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Sep. 30, 2016
Restricted stock units
Compensation expense related to the amortization of all equity - based compensation awards					$ 500,000	$ 300,000
Total unamortized compensation expense							$ 3,100,000	$ 1,500,000
Restricted Stock Units
Restricted stock units
Award outstanding at the end of the period (in shares)	28,567				28,567		27,521	28,567
Direct cost to the recipients of the restricted stock units					$ 0
Number of Shares
Nonvested restricted stock units at the beginning of the period (in shares)	28,567				28,567
Granted (in shares)					13,000
Vested (in shares)					(14,046)
Nonvested restricted stock units at the end of the period (in shares)					27,521
Weighted Average Fair Value
Nonvested restricted stock units at the beginning of the period (in dollars per share)	$ 90.96				$ 90.96
Granted (in dollars per share)					91.65
Vested (in dollars per share)					94.70
Nonvested restricted stock units at the end of the period (in dollars per share)					$ 115.30
Vested (in shares)					14,046
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)					1,320		1,320
Fair value of non-vested awards at the end of the period							$ 152,000
Number of Shares
Granted (in shares)				17,600
Vested (in shares)					(16,280)
Nonvested restricted stock units at the end of the period (in shares)					1,320
Weighted Average Fair Value
Vested (in shares)					16,280
Units scheduled to vest							1,320
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)					4,334		4,334
Fair value of non-vested awards at the end of the period							$ 500,000
Number of Shares
Granted (in shares)			13,000
Vested (in shares)					(8,666)
Nonvested restricted stock units at the end of the period (in shares)					4,334
Weighted Average Fair Value
Vested (in shares)					8,666
Units scheduled to vest							4,334
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)					8,867		8,867
Fair value of non-vested awards at the end of the period							$ 1,022,000
Number of Shares
Granted (in shares)		13,250
Vested (in shares)					(4,383)
Nonvested restricted stock units at the end of the period (in shares)					8,867
Weighted Average Fair Value
Vested (in shares)					4,383
Restricted Stock Units Awarded October 2015 | Vesting of awards in two anniversaries from the date of grant
Weighted Average Fair Value
Units scheduled to vest							4,333
Restricted Stock Units Awarded October 2015 | Vesting of awards in three anniversaries from the date of grant
Weighted Average Fair Value
Units scheduled to vest							4,334
Restricted Stock Units Awarded October 2015 | Vesting of awards equally in two through five anniversaries from the date of grant
Weighted Average Fair Value
Units scheduled to vest							200
Restricted Stock Units Awarded October 2016
Restricted stock units
Service period	36 months
Estimated fair value of award at grant date	$ 1,191,000
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							$ 1,499,000
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 Awarded October 2016 | Vesting of awards equally in three anniversaries from the date of grant
Weighted Average Fair Value
Units scheduled to vest							13,000
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