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
3 Months Ended 12 Months Ended
Mar. 31, 2020
Dec. 31, 2019
Feb. 04, 2020
Debt Instrument [Line Items]      
Debt Issuance Costs $ (47) $ (40)  
Total debt and finance lease obligations 4,925 5,119  
Less current portion (17) (18)  
Long-term portion of debt and finance lease obligations 4,908 5,101  
4.375% Senior Secured Notes due 2023, net of original issue discount      
Debt Instrument [Line Items]      
Debt and Lease Obligation $ 500 500  
Debt Instrument, Interest Rate, Stated Percentage 5.125%    
4.85% Senior Secured Notes due 2024, net of original issue discount      
Debt Instrument [Line Items]      
Debt and Lease Obligation $ 750 750  
Debt Instrument, Interest Rate, Stated Percentage 4.375%    
4.45% Senior Secured Notes due 2025, net of original issue discount      
Debt Instrument [Line Items]      
Debt and Lease Obligation $ 600 600  
Debt Instrument, Interest Rate, Stated Percentage 4.85%    
4.75% Senior Secured Notes due 2027      
Debt Instrument [Line Items]      
Debt and Lease Obligation $ 599 599  
Debt Instrument, Interest Rate, Stated Percentage 4.45%    
4.75% Senior Secured Notes [Member] [Member]      
Debt Instrument [Line Items]      
Debt and Lease Obligation $ 575 0 $ 575
Debt Instrument, Interest Rate, Stated Percentage 4.75%   4.75%
5.45% Senior Secured Notes due 2034, net of original issue discount      
Debt Instrument [Line Items]      
Debt and Lease Obligation $ 399 399  
Debt Instrument, Interest Rate, Stated Percentage 5.45%    
5.95% Senior Secured Notes due 2043, net of original issue discount      
Debt Instrument [Line Items]      
Debt and Lease Obligation $ 300 300  
Debt Instrument, Interest Rate, Stated Percentage 5.95%    
6.375% Senior Secured Notes [Member]      
Debt Instrument [Line Items]      
Debt and Lease Obligation $ 225 225  
Debt Instrument, Interest Rate, Stated Percentage 6.375%    
6.25% Senior Secured Notes [Member]      
Debt Instrument [Line Items]      
Debt and Lease Obligation $ 500 500  
Debt Instrument, Interest Rate, Stated Percentage 6.25%    
Senior secured credit facility      
Debt Instrument [Line Items]      
Debt and Lease Obligation $ 350 1,105  
Finance lease obligations      
Debt Instrument [Line Items]      
Debt and Lease Obligation $ 174 $ 181