Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements (Summary of Financial Instruments at Carrying and Fair Value) (Details)

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Fair Value Measurements (Summary of Financial Instruments at Carrying and Fair Value) (Details) - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Second Lien Notes    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Debt instrument, interest rate, stated (as a percent) 9.00%  
6.25% Senior Notes    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Debt instrument, interest rate, stated (as a percent) 6.25%  
6.125% Senior Notes due 2024    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Debt instrument, interest rate, stated (as a percent) 6.125%  
Unsecured debt | 6.25% Senior Notes    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Debt instrument, interest rate, stated (as a percent) 6.25%  
Unsecured debt | 6.125% Senior Notes due 2024    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Debt instrument, interest rate, stated (as a percent) 6.125%  
Unsecured debt | 8.25% Senior Notes    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Debt instrument, interest rate, stated (as a percent) 8.25%  
Unsecured debt | 6.375% Senior Notes    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Debt instrument, interest rate, stated (as a percent) 6.375%  
Carrying Value | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total $ 2,027,641 $ 2,027,641
Carrying Value | Level 2 | Unsecured debt | Second Lien Notes    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Senior Notes 516,659 516,659
Carrying Value | Level 2 | Unsecured debt | 6.25% Senior Notes    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Senior Notes 542,720 542,720
Carrying Value | Level 2 | Unsecured debt | 6.125% Senior Notes due 2024    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Senior Notes 460,241 460,241
Carrying Value | Level 2 | Unsecured debt | 8.25% Senior Notes    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Senior Notes 187,238 187,238
Carrying Value | Level 2 | Unsecured debt | 6.375% Senior Notes    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Senior Notes 320,783 320,783
Fair Value | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Total 1,810,912 1,336,990
Fair Value | Level 2 | Unsecured debt | Second Lien Notes    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Senior Notes 524,409 470,160
Fair Value | Level 2 | Unsecured debt | 6.25% Senior Notes    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Senior Notes 483,021 344,627
Fair Value | Level 2 | Unsecured debt | 6.125% Senior Notes due 2024    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Senior Notes 388,904 260,036
Fair Value | Level 2 | Unsecured debt | 8.25% Senior Notes    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Senior Notes 161,961 100,172
Fair Value | Level 2 | Unsecured debt | 6.375% Senior Notes    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Senior Notes $ 252,617 $ 161,995