Quarterly report pursuant to Section 13 or 15(d)

Long-Term Debt (Debt) (Details)

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Long-Term Debt (Debt) (Details) - USD ($)
$ in Millions
Jun. 30, 2018
Dec. 31, 2017
Debt Instrument [Line Items]    
Build to suit lease obligation $ 100 $ 101
Less debt issuance costs, net (20) (22)
Total debt and capital lease obligations 5,040 5,190
Less current portion (417) (17)
Long-term portion of debt and capital lease obligations $ 4,623 5,173
3.125% Senior Secured Notes due 2019, net of original issue discount    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Stated Percentage 3.125%  
Debt and Capital Lease Obligations $ 399 399
5.125% Senior Secured Notes due 2022    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Stated Percentage 5.125%  
Debt and Capital Lease Obligations $ 500 500
4.375% Senior Secured Notes due 2023, net of original issue discount    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Stated Percentage 4.375%  
Debt and Capital Lease Obligations $ 750 750
4.85% Senior Secured Notes due 2024, net of original issue discount    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Stated Percentage 4.85%  
Debt and Capital Lease Obligations $ 600 600
4.45% Senior Secured Notes due 2025, net of original issue discount    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Stated Percentage 4.45%  
Debt and Capital Lease Obligations $ 599 599
5.45% Senior Secured Notes due 2034, net of original issue discount    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Stated Percentage 5.45%  
Debt and Capital Lease Obligations $ 399 399
5.95% Senior Secured Notes due 2043, net of original issue discount    
Debt Instrument [Line Items]    
Debt Instrument, Interest Rate, Stated Percentage 5.95%  
Debt and Capital Lease Obligations $ 300 300
Senior secured credit facility    
Debt Instrument [Line Items]    
Debt and Capital Lease Obligations 1,335 1,496
Capital lease obligations    
Debt Instrument [Line Items]    
Debt and Capital Lease Obligations $ 78 $ 68