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, 2017
Dec. 31, 2016
Dec. 21, 2016
Oct. 31, 2016
Oct. 14, 2016
Jun. 04, 2015
Apr. 21, 2015
Debt Instrument [Line Items]              
Net unamortized debt issuance costs $ (30,111) $ (27,174)          
Less: current maturities of long term debt (570) (276)          
Long-term debt, net of current maturities 1,958,136 1,593,599          
Construction loans              
Debt Instrument [Line Items]              
Net unamortized debt issuance costs (100)            
7.75% Senior Notes due 2020 | Senior notes              
Debt Instrument [Line Items]              
Long-term debt $ 0 0          
Stated interest rate, percent 7.75%            
6.625% Senior Notes due 2023 | Senior notes              
Debt Instrument [Line Items]              
Long-term debt $ 350,000 350,000          
Net unamortized debt issuance costs $ (5,500)            
Stated interest rate, percent 6.625%           6.625%
6.000% Senior Notes due 2024 | Senior notes              
Debt Instrument [Line Items]              
Long-term debt $ 650,000 650,000          
Net unamortized debt issuance costs $ (10,200)            
Stated interest rate, percent 6.00%     6.00% 6.00%    
6.375% Senior Notes due 2025 | Senior notes              
Debt Instrument [Line Items]              
Long-term debt $ 600,000 600,000          
Net unamortized debt issuance costs $ (14,300)            
Stated interest rate, percent 6.375%   6.375%        
Nova Scotia, Amegy, KeyBank | Revolving credit agreement | Amended and restated credit agreement              
Debt Instrument [Line Items]              
Long-term debt $ 365,000 0          
InterBank | Revolving credit agreement | Construction loans              
Debt Instrument [Line Items]              
Stated interest rate, percent           4.50%  
InterBank | Letter of credit | Construction loans              
Debt Instrument [Line Items]              
Long-term debt $ 23,817 $ 21,049