XML 45 R34.htm IDEA: XBRL DOCUMENT v3.7.0.1
Debt (Summary of Senior Notes) (Details) - USD ($)
Mar. 31, 2017
Dec. 31, 2016
Feb. 29, 2016
Debt Instrument [Line Items]      
Net premiums, discounts, and issuance costs $ (12,996,000) $ (12,984,000)  
Senior notes 3,110,004,000 3,110,016,000  
Estimated fair value $ 3,206,575,000 $ 3,112,297,000  
7.625% unsecured senior notes due October 2017 | Senior Notes      
Debt Instrument [Line Items]      
Stated interest rate 7.625% 7.625%  
Face amount $ 123,000,000 $ 123,000,000  
4.250% unsecured senior notes due March 2021 | Senior Notes      
Debt Instrument [Line Items]      
Stated interest rate 4.25% 4.25% 4.25%
Face amount $ 700,000,000 $ 700,000,000 $ 300,000,000
5.500% unsecured senior notes due March 2026 | Senior Notes      
Debt Instrument [Line Items]      
Stated interest rate 5.50% 5.50%  
Face amount $ 700,000,000 $ 700,000,000  
5.000% unsecured senior notes due January 2027 | Senior Notes      
Debt Instrument [Line Items]      
Stated interest rate 5.00% 5.00%  
Face amount $ 600,000,000 $ 600,000,000  
7.875% unsecured senior notes due June 2032 | Senior Notes      
Debt Instrument [Line Items]      
Stated interest rate 7.875% 7.875%  
Face amount $ 300,000,000 $ 300,000,000  
6.375% unsecured senior notes due May 2033 | Senior Notes      
Debt Instrument [Line Items]      
Stated interest rate 6.375% 6.375%  
Face amount $ 400,000,000 $ 400,000,000  
6.000% unsecured senior notes due February 2035 | Senior Notes      
Debt Instrument [Line Items]      
Stated interest rate 6.00% 6.00%  
Face amount $ 300,000,000 $ 300,000,000