Quarterly report pursuant to Section 13 or 15(d)

Debt (Schedule of Debt) (Details)

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Debt (Schedule of Debt) (Details) - USD ($)
Jun. 30, 2017
Dec. 31, 2016
Nov. 30, 2016
Debt Instrument [Line Items]      
Fair value of interest rate swap agreements $ (48,000,000) $ (58,000,000)  
Total senior notes 4,559,000,000 4,550,000,000  
Mortgage notes payable 63,000,000 64,000,000  
Capital leases and other 18,000,000 18,000,000  
Debt issuance costs (70,000,000) (77,000,000)  
Total debt 4,720,000,000 4,655,000,000  
Less current portion (4,000,000) (4,000,000)  
Long-term debt 4,716,000,000 4,651,000,000  
Revolving credit agreement      
Debt Instrument [Line Items]      
Revolving credit agreement 150,000,000 100,000,000  
Senior Notes | $1,400 million 5.625% Senior notes, due February 15, 2021      
Debt Instrument [Line Items]      
Debt, face amount $ 1,400,000,000    
Interest rate, stated 5.625%    
Senior notes $ 1,400,000,000 1,400,000,000  
Senior Notes | $1,000 million 4.75% Senior notes, due May 15, 2022      
Debt Instrument [Line Items]      
Debt, face amount $ 1,000,000,000    
Interest rate, stated 4.75%    
Senior notes $ 1,007,000,000 1,008,000,000  
Senior Notes | $1,000 million 6.125% Senior notes, due February 15, 2024      
Debt Instrument [Line Items]      
Debt, face amount $ 1,000,000,000    
Interest rate, stated 6.125%    
Senior notes $ 1,000,000,000 1,000,000,000  
Senior Notes | $1,200 million 4.75% Senior notes, due January 15, 2025      
Debt Instrument [Line Items]      
Debt, face amount $ 1,200,000,000   $ 1,200,000,000
Interest rate, stated 4.75%   4.75%
Senior notes $ 1,200,000,000 $ 1,200,000,000