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 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 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 $ (31) $ 18 $ 180 $ (43)  
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 $ (25) 56 $ 133 76  
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 26 (42) (77) (236)  
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 (41) 6 76 130  
Other derivatives          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Realized and unrealized gains (losses) on financial instruments, net $ 9 $ (2) $ 48 $ (13)