STOCK PLANS AND STOCK BASED COMPENSATION (Details) - USD ($)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
STOCK PLANS AND STOCK BASED COMPENSATION      
Number of shares available for grant permitted by plan 3,000,000    
Weighted average assumptions used to determined fair value of stock options granted      
Risk-free interest rate (as a percent) 1.43% 1.54% 2.11%
Expected dividend yield (as a percent) 3.16% 3.06% 3.18%
Expected stock price volatility (as a percent) 20.17% 22.66% 30.20%
Expected life of options 5 years 5 years 6 years
Information related to the stock option plan      
Weighted-average fair value per share of options granted (in dollars per share) $ 3.27 $ 3.58 $ 5.16
Information related to stock option and restricted stock awards granted      
Expenses $ 1,030,000 $ 422,000 $ 458,000
Estimated unrecognized stock option and restricted stock award expense related to unvested options and awards (net of estimated forfeitures)      
2017 1,039,000    
2018 591,000    
2019 155,000    
2020 40,000    
2021 3,000    
Total $ 1,828,000    
Minimum      
STOCK PLANS AND STOCK BASED COMPENSATION      
Vesting period 3 years    
Exercisable period 5 years    
Maximum      
STOCK PLANS AND STOCK BASED COMPENSATION      
Exercisable period 6 years    
Stock option      
STOCK PLANS AND STOCK BASED COMPENSATION      
Exercisable period 1 year    
Options      
Outstanding, beginning of year (in shares) 323,400 155,000  
Granted (in shares) 5,000 323,400  
Exercised (in shares) (4,000) (97,750)  
Forfeited or expired (in shares) (11,800) (57,250)  
Outstanding, end of year (in shares) 312,600 323,400 155,000
Fully vested and expected to vest (in shares) 312,600    
Exercisable (vested) at end of year (in shares) 4,000    
Weighted Average Exercise Price      
Outstanding, beginning of year (in dollars per share) $ 24.40 $ 20.15  
Granted (in dollars per share) 26.43 24.51  
Exercised (in dollars per share) 20.12 19.77  
Forfeited or expired (in dollars per share) 24.47 21.43  
Outstanding, end of year (in dollars per share) 24.49 $ 24.40 $ 20.15
Fully vested and expected to vest (in dollars per share) 24.49    
Exercisable (vested) at end of year (in dollars per share) $ 20.77    
Weighted Average Remaining Contractual Term      
Outstanding, end of year 3 years 9 months 7 days 4 years 8 months 12 days  
Fully vested and expected to vest 3 years 9 months 7 days    
Exercisable (vested) at end of year 2 months 19 days    
Aggregate Intrinsic Value      
Outstanding, end of year $ 4,705,807 $ 650,000  
Fully vested and expected to vest 4,705,807    
Exercisable (vested) at end of year 75,080    
Information related to the stock option plan      
Intrinsic value of options exercised 18,000 581,000 $ 356,000
Cash received from options exercised, net of shares redeemed $ 80,000 $ 1,136,000 $ 1,103,000
Weighted-average fair value per share of options granted (in dollars per share) $ 3.27 $ 3.58 $ 5.16
Information related to stock option and restricted stock awards granted      
Expenses $ 248,000 $ 169,000 $ 53,000
Estimated unrecognized stock option and restricted stock award expense related to unvested options and awards (net of estimated forfeitures)      
2017 258,000    
2018 120,000    
2019 12,000    
2020 8,000    
2021 2,000    
Total 400,000    
Stock option | Non-executive officer employees      
Information related to the stock option plan      
Outstanding loans $ 371,000 $ 660,000  
Stock option | Class B Common Stock      
Options      
Exercisable (vested) at end of year (in shares) 0    
Restricted Stock Awards      
Shares      
Outstanding, beginning of year (in shares) 79,000 80,500  
Granted (in shares)   2,500  
Forfeited (in shares) (2,000) (4,000)  
Outstanding, end of year (in shares) 77,000 79,000 80,500
Fully vested and expected to vest (in shares) 77,000    
Weighted-average grant date fair value      
Outstanding, beginning of year (in dollars per share) $ 20.02 $ 19.85  
Granted (in dollars per share)   25.19  
Forfeited (in dollars per share) 19.85 19.85  
Outstanding, end of year (in dollars per share) 20.02 $ 20.02 $ 19.85
Fully vested and expected to vest (in dollars per share) $ 20.02    
Information related to stock option and restricted stock awards granted      
Expenses $ 258,000 $ 253,000 $ 405,000
Estimated unrecognized stock option and restricted stock award expense related to unvested options and awards (net of estimated forfeitures)      
2017 253,000    
2018 251,000    
2019 143,000    
2020 32,000    
2021 1,000    
Total $ 680,000    
Restricted Stock Awards | Minimum      
Shares      
Unrecognized compensation expense recognition period 5 years    
Restricted Stock Awards | Maximum      
Shares      
Unrecognized compensation expense recognition period 6 years    
Performance Stock Units      
STOCK PLANS AND STOCK BASED COMPENSATION      
Vesting period 4 years    
Shares      
Granted (in shares) 55,000    
Outstanding, end of year (in shares) 55,000    
Fully vested and expected to vest (in shares) 55,000    
Weighted-average grant date fair value      
Granted (in dollars per share) $ 23.13    
Outstanding, end of year (in dollars per share) 23.13    
Fully vested and expected to vest (in dollars per share) $ 23.13    
Information related to stock option and restricted stock awards granted      
Expenses $ 524,000    
Estimated unrecognized stock option and restricted stock award expense related to unvested options and awards (net of estimated forfeitures)      
2017 528,000    
2018 220,000    
Total $ 748,000    
Performance Stock Units | Tranche One      
Information related to stock option and restricted stock awards granted      
Return on average assets (as a percent) 1.25%    
Vesting rights (as a percent) 50.00%    
Performance Stock Units | Tranche Two      
Information related to stock option and restricted stock awards granted      
Return on average assets (as a percent) 1.25%    
Vesting rights (as a percent) 50.00%