Quarterly report pursuant to Section 13 or 15(d)

LONG-TERM DEBT (Break-Down of Long-Term Debt) (Details)

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LONG-TERM DEBT (Break-Down of Long-Term Debt) (Details) - USD ($)
$ in Thousands
Sep. 30, 2018
Dec. 31, 2017
Oct. 11, 2017
Dec. 21, 2016
Oct. 14, 2016
Jun. 04, 2015
Apr. 21, 2015
Debt Instrument [Line Items]              
Net unamortized debt issuance costs $ (31,824) $ (34,781)          
Less: current maturities of long term debt (647) (622)          
Long-term debt, net of current maturities 2,100,825 2,038,321          
Construction loan              
Debt Instrument [Line Items]              
Net unamortized debt issuance costs (100)            
6.625% senior unsecured notes due 2023 | Senior notes              
Debt Instrument [Line Items]              
Long-term debt 350,000 350,000          
Net unamortized debt issuance costs $ (4,600)            
Stated interest rate, percent 6.625%           6.625%
6.000% senior unsecured notes due 2024 | Senior notes              
Debt Instrument [Line Items]              
Long-term debt $ 650,000 650,000          
Net unamortized debt issuance costs $ (9,000)            
Stated interest rate, percent 6.00%       6.00%    
6.375% senior unsecured notes due 2025 | Senior notes              
Debt Instrument [Line Items]              
Long-term debt $ 600,000 600,000          
Net unamortized debt issuance costs $ (12,900)            
Stated interest rate, percent 6.375%     6.375%      
6.375% senior unsecured notes due 2026 | Senior notes              
Debt Instrument [Line Items]              
Long-term debt $ 450,000 450,000          
Net unamortized debt issuance costs $ (5,200)            
Stated interest rate, percent 6.375%   6.375%        
Nova Scotia, Amegy, KeyBank | Revolving credit agreement | Revolving credit agreement              
Debt Instrument [Line Items]              
Long-term debt $ 60,000 0          
InterBank | Revolving credit agreement | Construction loan              
Debt Instrument [Line Items]              
Stated interest rate, percent           4.50%  
InterBank | Letter of credit | Construction loan              
Debt Instrument [Line Items]              
Long-term debt $ 23,296 $ 23,724