Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.2
Fair Value Measurements (Summary of Financial Instruments at Carrying and Fair Value) (Details) - USD ($)
$ in Thousands
Jun. 30, 2019
Dec. 31, 2018
Jun. 07, 2018
6.125% senior unsecured notes due 2024      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Debt instrument, interest rate, stated (as a percent) 6.125%    
6.125% senior unsecured notes due 2024 | Unsecured debt      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Debt instrument, interest rate, stated (as a percent) 6.125%    
6.375% senior unsecured notes due 2026      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Debt instrument, interest rate, stated (as a percent) 6.375%    
6.375% senior unsecured notes due 2026 | Unsecured debt      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Debt instrument, interest rate, stated (as a percent)     6.375%
Carrying Value      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Credit Facility $ 105,000 $ 200,000  
Total 1,095,260 1,189,473  
Carrying Value | 6.125% senior unsecured notes due 2024 | Unsecured debt      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Senior Notes 596,154 595,788  
Carrying Value | 6.375% senior unsecured notes due 2026 | Unsecured debt      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Senior Notes 394,106 393,685  
Fair Value      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Credit Facility 105,000 200,000  
Total 1,118,036 1,130,000  
Fair Value | 6.125% senior unsecured notes due 2024 | Unsecured debt      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Senior Notes 609,048 558,000  
Fair Value | 6.375% senior unsecured notes due 2026 | Unsecured debt      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Senior Notes $ 403,988 $ 372,000