STOCK COMPENSATION PLANS (Details) | 3 Months Ended | 6 Months Ended | 9 Months Ended | 12 Months Ended | | |
Sep. 30, 2016USD ($)$ / sharesshares | Jun. 30, 2016USD ($)$ / sharesshares | Sep. 30, 2016USD ($)Director$ / sharesshares | Sep. 30, 2015USD ($) | Dec. 31, 2014 | May 04, 2016$ / sharesshares | Dec. 18, 2015$ / sharesshares |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | | | | | | | |
Number of directors in committee | Director | | | 3 | | | | |
Non-vested shares of Class A Stock under option [Abstract] | | | | | | | |
Vesting period for granted option | | | 1 year | | | | |
Options granted term | | | 10 years | | | | |
Weighted-average assumptions used for grants issued [Abstract] | | | | | | | |
Expected Dividend Yield | | | | | 3.88% | | |
Expected Stock Price Volatility | | | | | 26.50% | | |
Weighted Average Risk-Free Interest Rate | | | | | 2.24% | | |
Weighted Average Expected Life of Options | | | | | 7 years 6 months 7 days | | |
Restricted Stock [Member] | | | | | | | |
Share Based Compensation Arrangement By Share Based Payment Award Nonvested Options Outstanding [Roll Forward] | | | | | | | |
Outstanding at beginning of period, Non-vested option shares (in shares) | shares | | 0 | 0 | | | | |
Granted, option shares (in shares) | shares | | | 5,000 | | | | |
Vested, option shares (in shares) | shares | | | 0 | | | | |
Cancelled, option shares (in shares) | shares | | | 0 | | | | |
Outstanding at end of period, Non-vested option shares (in shares) | shares | 5,000 | | 5,000 | | | | |
Non-vested shares of Class A Stock under option [Abstract] | | | | | | | |
Outstanding at beginning of period, weighted average grant-date fair value per option (in dollars per share) | $ / shares | | $ 0 | $ 0 | | | | |
Granted, weighted average grant-date fair value per option (in dollars per share) | $ / shares | | | 27.7 | | | | |
Vested, weighted average grant-date fair value per option (in dollars per share) | $ / shares | | | 0 | | | | |
Cancelled, weighted average grant-date fair value per option (in dollars per share) | $ / shares | | | 0 | | | | |
Outstanding at end of period, weighted average grant-date fair value per option (in dollars per share) | $ / shares | $ 27.7 | | $ 27.7 | | | | |
Class A Stock [Member] | 2005 Equity Compensation Plan [Member] | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | | | | | | | |
Compensation expense | $ | | | | $ 46,000 | | | |
Class A Stock [Member] | 2015 Equity Compensation Plan [Member] | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | | | | | | | |
Compensation expense | $ | $ 35,000 | | $ 57,000 | | | | |
Unrecognized expense related to non-vested option shares | $ | $ 0 | | $ 0 | | | | |
Number of shares authorizes under the plan (in shares) | shares | | | | | | 5,000 | 5,000 |
Fair market value (in dollars per share) | $ / shares | | | | | | $ 27.7 | $ 27.38 |
Class A Stock [Member] | Stock Options [Member] | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] | | | | | | | |
Outstanding at beginning of period, option shares (in shares) | shares | | 270,000 | 270,000 | | | | |
Granted, option shares (in shares) | shares | | | 0 | | | | |
Exercised/vested and released, option shares (in shares) | shares | | | (33,750) | | | | |
Expired, option shares (in shares) | shares | | | 0 | | | | |
Outstanding at end of period, option shares (in shares) | shares | 236,250 | | 236,250 | | | | |
Exercisable/vested at end of period, option share (in shares) | shares | 236,250 | | 236,250 | | | | |
Shares of Class A Non-Voting Common Stock under option [Abstract] | | | | | | | |
Outstanding at beginning of period, weighted average exercise price (in dollars per shares) | $ / shares | | $ 19.34 | $ 19.34 | | | | |
Granted, weighted average exercise price (in dollars per share) | $ / shares | | | 0 | | | | |
Exercised/vested and released, weighted average exercise price (in dollars per shares) | $ / shares | | | 19.64 | | | | |
Expired/cancelled, weighted average exercise price (in dollars per share) | $ / shares | | | 0 | | | | |
Outstanding at end of period, weighted average exercise price (in dollars per shares) | $ / shares | $ 19.30 | | 19.30 | | | | |
Exercisable/vested at end of period, weighted average exercise price (in dollars per shares) | $ / shares | $ 19.30 | | $ 19.30 | | | | |
Outstanding at end of period, weighted average remaining life | | | 4 years 7 months 2 days | | | | |
Exercisable/vested at end of period, weighted average remaining life | | | 4 years 7 months 2 days | | | | |
Outstanding at beginning of period, aggregate intrinsic value | $ | | $ 2,256,000 | $ 2,256,000 | | | | |
Granted, aggregate intrinsic value | $ | | | 0 | | | | |
Exercised/ vested and released, aggregate intrinsic value | $ | | | 286,000 | | | | |
Expired/cancelled, aggregate intrinsic value | $ | | $ 0 | | | | | |
Outstanding at end of period, aggregate intrinsic value | $ | $ 2,182,000 | | 2,182,000 | | | | |
Exercisable/vested at end of period, aggregate intrinsic value | $ | $ 2,182,000 | | $ 2,182,000 | | | | |
Class A Stock [Member] | Restricted Stock [Member] | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] | | | | | | | |
Outstanding at beginning of period, option shares (in shares) | shares | | 0 | 0 | | | | |
Granted, option shares (in shares) | shares | | 5,000 | | | | | |
Exercised/vested and released, option shares (in shares) | shares | | 0 | | | | | |
Expired, option shares (in shares) | shares | | 0 | | | | | |
Outstanding at end of period, option shares (in shares) | shares | 5,000 | | 5,000 | | | | |
Exercisable/vested at end of period, option share (in shares) | shares | 0 | | 0 | | | | |
Shares of Class A Non-Voting Common Stock under option [Abstract] | | | | | | | |
Outstanding at beginning of period, weighted average exercise price (in dollars per shares) | $ / shares | | $ 0 | $ 0 | | | | |
Granted, weighted average exercise price (in dollars per share) | $ / shares | | | 27.70 | | | | |
Exercised/vested and released, weighted average exercise price (in dollars per shares) | $ / shares | | | 0 | | | | |
Expired/cancelled, weighted average exercise price (in dollars per share) | $ / shares | | | 0 | | | | |
Outstanding at end of period, weighted average exercise price (in dollars per shares) | $ / shares | $ 27.70 | | 27.70 | | | | |
Exercisable/vested at end of period, weighted average exercise price (in dollars per shares) | $ / shares | $ 0 | | $ 0 | | | | |
Class A Stock [Member] | Restricted Stock [Member] | 2015 Equity Compensation Plan [Member] | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | | | | | | | |
Unrecognized expense related to non-vested option shares | $ | $ 82,000 | | $ 82,000 | | | | |
Period over which unvested options cost will recognized | | | 7 months 2 days | | | | |