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EMPLOYEE RETIREMENT PLANS - Additional Information (Details)
12 Months Ended
Dec. 31, 2018
USD ($)
participant
multiple
denominator
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Defined Benefit Plan Disclosure [Line Items]      
Maximum contribution percentage (in hundredths) 90.00%    
Matching contribution limit (in hundredths) 3.00%    
Contributions to the 401(k) Plan $ 1,200,000 $ 601,000 $ 459,000
Initial prior service cost for retirement plan   280,000  
Prior service cost expected to be amortized in next fiscal year $ 1,595,000    
Supplemental Executive Retirement Plan [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Number of participants | participant 7    
Factor used to determine annual base salary | multiple 12    
Annual base salary period (in months) 24 months    
Age of participant (in years) 65 years    
Minimum period of service (in years) 20 years    
Benefit percentage, tier one (in hundredths) 50.00%    
Benefit percentage, tier two (in hundredths) 25.00%    
Benefit percentage, tier three (in hundredths) 15.00%    
Minimum period of service for prorated benefit (in years) 15 years    
Factor used to determine prorated benefit | denominator 20    
Installment period (in years) 10 years    
Benefit percentage for special participants (in hundredths) 50.00%    
Initial prior service cost for retirement plan $ 20,400,000    
Prior service cost expected to be amortized in next fiscal year 3,200,000    
Accumulated benefit obligation $ 41,300,000 $ 30,400,000  
Defined benefit plan threshold of benefit obligation at which actuarial losses are amortized (in hundredths) 10.00%