BENEFIT PLANS (Details)
12 Months Ended
Dec. 31, 2016
USD ($)
employee
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
401 (k) plan      
Minimum percentage of annual eligible compensation by the participants 1.00%    
Maximum percentage of annual eligible compensation by the participants 75.00%    
Percentage of employers matching contribution for participant contributions up to 1% 100.00%    
Percentage of additional employers matching contribution 75.00%    
Vesting period 2 years    
Normal and bonus contributions      
Employer matching contributions $ 1,803,000 $ 1,517,000 $ 1,419,000
Discretionary employer bonus matching contributions $ 582,000    
Supplemental Employee Retirement Plan      
Normal and bonus contributions      
Number of participants under SERP | employee 4    
SERP liability incurred $ 2,000,000    
Employer matching contributions $ 81,000    
Minimum      
401 (k) plan      
Percentage of participant contributions up to which employer matches additional 75% contribution 2.00%    
Maximum      
401 (k) plan      
Percentage of participant contributions up to which employer matches 100% contribution 1.00%    
Percentage of participant contributions up to which employer matches additional 75% contribution 5.00%