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DEBT - Additional Information (Details)
Feb. 28, 2017
Mar. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Nov. 08, 2017
USD ($)
Mar. 01, 2017
Debt Instrument [Line Items]          
Current portion of long-term debt   $ 430,000 $ 425,000    
Bank of America, N.A. | Line of Credit | Revolving Credit Facility          
Debt Instrument [Line Items]          
Consolidated interest coverage ratio (not less than)         2.75
Minimum liquidity required (at least)         0.2
Bank of America, N.A. | Line of Credit | Revolving Credit Facility | Period Five          
Debt Instrument [Line Items]          
Consolidated funded debt to consolidated EBITDA ratio         2.50
Bank of America, N.A. | Line of Credit | Revolving Credit Facility | Period Six          
Debt Instrument [Line Items]          
Consolidated funded debt to consolidated EBITDA ratio         2.75
Bank of America, N.A. | Line of Credit | Revolving Credit Facility | Period Seven          
Debt Instrument [Line Items]          
Consolidated funded debt to consolidated EBITDA ratio         3.00
Bank of America, N.A. | Line of Credit | Revolving Credit Facility | Period Eight          
Debt Instrument [Line Items]          
Consolidated funded debt to consolidated EBITDA ratio         3.50
Bank of America, N.A. | Line of Credit | Revolving Credit Facility | Period Nine          
Debt Instrument [Line Items]          
Consolidated funded debt to consolidated EBITDA ratio         3.00
Bank of America, N.A. | Line of Credit | Revolving Credit Facility | Period Ten          
Debt Instrument [Line Items]          
Consolidated funded debt to consolidated EBITDA ratio         2.75
Bank of America, N.A. | Line of Credit | Revolving Credit Facility | Period Eleven          
Debt Instrument [Line Items]          
Consolidated funded debt to consolidated EBITDA ratio         2.50
4.20% Building Loan | Secured Debt          
Debt Instrument [Line Items]          
Current portion of long-term debt   $ 400,000      
Interest rate   4.20%      
Fifth Amended and Restated Credit Agreement | Bank of America, N.A. | Revolving Credit Facility          
Debt Instrument [Line Items]          
Long-term line of credit   $ 0      
Fifth Amended and Restated Credit Agreement | Bank of America, N.A. | Letter of Credit          
Debt Instrument [Line Items]          
Outstanding borrowing under bank credit facility   9,800,000      
Remaining borrowing capacity   $ 90,200,000      
Fifth Amended and Restated Credit Agreement | Bank of America, N.A. | Line of Credit | Revolving Credit Facility          
Debt Instrument [Line Items]          
Available for borrowing       $ 100,000,000  
Fifth Amended and Restated Credit Agreement | Bank of America, N.A. | Line of Credit | Revolving Credit Facility | Base Rate | Minimum          
Debt Instrument [Line Items]          
Percentage of borrowing base utilization, percent 2.00%        
Fifth Amended and Restated Credit Agreement | Bank of America, N.A. | Line of Credit | Revolving Credit Facility | Base Rate | Maximum          
Debt Instrument [Line Items]          
Percentage of borrowing base utilization, percent 3.00%        
Fifth Amended and Restated Credit Agreement | Bank of America, N.A. | Line of Credit | Revolving Credit Facility | LIBOR | Minimum          
Debt Instrument [Line Items]          
Percentage of borrowing base utilization, percent 3.00%        
Fifth Amended and Restated Credit Agreement | Bank of America, N.A. | Line of Credit | Revolving Credit Facility | LIBOR | Maximum          
Debt Instrument [Line Items]          
Percentage of borrowing base utilization, percent 4.00%