STOCK-BASED COMPENSATION- Activity of the stock incentive plans for options (Details) - Stock Incentive Plan - Stock Options - $ / shares
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Options Shares Outstanding      
Balance 746,004 967,859 793,157
Granted 170,500 162,000 221,000
Options assumed in acquisition $ 91,701    
Exercise of stock options (84,723) [1] (381,505) [1] (39,548)
Forfeited (1,456) (2,350) (6,750)
Balance 922,026 746,004 967,859
Weighted-Average Exercise Price      
Balance $ 21.56 $ 19.30 $ 17.86
Granted $ 36.86 26.66 23.80
Options assumed in acquisition 21.03    
Exercise of stock options $ 20.98 [1] 18.00 [1] 16.01
Forfeited 21.71 19.61 16.80
Balance $ 24.39 $ 21.56 $ 19.30
Exercisable Shares, Beginning Balance 325,979 630,121 600,846
Exercisable Shares, Ending Balance 439,639 325,979 630,121
Weighted Average Exercise Price, Beginning Balance $ 19.09 $ 18.24 $ 18.25
Weighted Average Exercise Price, Ending Balance $ 19.97 $ 19.09 $ 18.24
[1] The terms of the stock option agreements permit having a number of shares of stock withheld, the fair market value of which as of the date of exercise is sufficient to satisfy the exercise price and/or tax withholding requirements, and accordingly 10,244 shares and 167,779 shares were surrendered in 2016 and 2015, respectively, and no shares surrendered in 2014.