Annual report pursuant to Section 13 and 15(d)

EMPLOYEE BENEFITS AND STOCK BASED COMPENSATION (Narrative) (Details)

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EMPLOYEE BENEFITS AND STOCK BASED COMPENSATION (Narrative) (Details) - USD ($)
 12 Months Ended 58 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2016
Apr. 20, 2015
Defined Benefit Plan Disclosure [Line Items]          
Deferred compensation plans obligation to Board of Directors $ 11,100,000 $ 10,400,000   $ 10,400,000  
Maximum term of stock options 10 years        
Stock options granted 0 0   0  
Stock options term from the grant date 1 year 7 months 24 days        
Number of stock option awards exercised 63,476 88,409 60,637    
Intrinsic value of stock options exercised $ 1,200,000 $ 1,171,000 $ 544,000    
Fair value of stock options exercised 2,200,000 2,594,000 1,400,000    
Cash received from the exercise of stock options 1,000,000 1,423,000 886,000    
Tax benefit from exercise of equity-based awards 370,000 381,000 178,000    
Fair value of stock options vested $ 47,000 159,000 316,000    
Restricted stock vesting percentage 50.00%        
Intrinsic value of stock options outstanding $ 2,708,076 $ 3,900,000 $ 2,800,000 $ 3,900,000  
Unamortized compensation costs $ 9,089,000        
Minimum          
Defined Benefit Plan Disclosure [Line Items]          
Hours of service required for eligibility under plan 1000 hours        
1% through 3%          
Defined Benefit Plan Disclosure [Line Items]          
Percentage of employer's match for 401(k) plan 100.00%        
1% through 3% | Minimum          
Defined Benefit Plan Disclosure [Line Items]          
Percentage of employee's gross pay for 401(k) plan 1.00%        
1% through 3% | Maximum          
Defined Benefit Plan Disclosure [Line Items]          
Percentage of employee's gross pay for 401(k) plan 3.00%        
4% through 5%          
Defined Benefit Plan Disclosure [Line Items]          
Percentage of employer's match for 401(k) plan 50.00%        
4% through 5% | Minimum          
Defined Benefit Plan Disclosure [Line Items]          
Percentage of employee's gross pay for 401(k) plan 4.00%        
4% through 5% | Maximum          
Defined Benefit Plan Disclosure [Line Items]          
Percentage of employee's gross pay for 401(k) plan 5.00%        
Stock and Incentive Plan          
Defined Benefit Plan Disclosure [Line Items]          
Number of shares authorized to be issued, maximum 2,500,000        
Number of shares available for future issuance 1,560,728        
2011 Plan          
Defined Benefit Plan Disclosure [Line Items]          
Number of shares authorized to be issued, maximum         1,000,000
Restricted Stock | Minimum          
Defined Benefit Plan Disclosure [Line Items]          
Vesting period of restricted stock awards and performance stock units 3 years        
Restricted Stock | Maximum          
Defined Benefit Plan Disclosure [Line Items]          
Vesting period of restricted stock awards and performance stock units 4 years