Quarterly report pursuant to Section 13 or 15(d)

Assets And Liabilities Measured At Fair Value - Realized and Unrealized Gains (Losses) on Financial Instruments (Details)

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Assets And Liabilities Measured At Fair Value - Realized and Unrealized Gains (Losses) on Financial Instruments (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Oct. 17, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Realized and unrealized gains (losses) on financial instruments, net $ 58 $ (49) $ 211 $ (61)  
1.375% Cash Convertible Senior Notes Due 2023          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Debt instrument interest rate 1.375%   1.375%   1.375%
Marketable Securities          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Realized and unrealized gains (losses) on financial instruments, net $ 84 (10) $ 158 20  
Debt measured at fair value          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Realized and unrealized gains (losses) on financial instruments, net (133) (78) (103) (194)  
Bond Hedge Change in Fair Value          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Realized and unrealized gains (losses) on financial instruments, net 97 46 117 124  
Other derivatives          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Realized and unrealized gains (losses) on financial instruments, net $ 10 $ (7) $ 39 $ (11)