v3.10.0.1
Fair Value Measurement of Assets and Liabilities - Financial Assets and Liabilities Measured at Fair Value, Recurring (Details) - USD ($)
$ in Millions
Sep. 30, 2018
Dec. 31, 2017
Assets:    
Derivatives $ 73  
Liabilities:    
Derivatives 0  
Recurring    
Assets:    
Cash and cash equivalents 2,086 $ 2,120
Derivatives   28
Total financial assets 9,333 11,337
Recurring | Short-term Investments    
Assets:    
Investments, Fair Value Disclosure 2,752 3,743
Recurring | Other Current Assets    
Assets:    
Derivatives 363  
Recurring | Long-term Investments    
Assets:    
Investments, Fair Value Disclosure 4,132 5,446
Recurring | Other Current Liabilities    
Liabilities:    
Derivatives 55 29
Recurring | Restricted cash | Short-term Investments    
Assets:    
Investments, Fair Value Disclosure 15 20
Recurring | Corporate debt securities | Short-term Investments    
Assets:    
Investments, Fair Value Disclosure 2,696 3,723
Recurring | Corporate debt securities | Long-term Investments    
Assets:    
Investments, Fair Value Disclosure 4,132 5,446
Recurring | Government and agency securities | Short-term Investments    
Assets:    
Investments, Fair Value Disclosure 41  
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)    
Assets:    
Cash and cash equivalents 2,051 2,120
Derivatives   0
Total financial assets 2,066 2,140
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term Investments    
Assets:    
Investments, Fair Value Disclosure 15 20
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Current Assets    
Assets:    
Derivatives 0  
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Long-term Investments    
Assets:    
Investments, Fair Value Disclosure 0 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other Current Liabilities    
Liabilities:    
Derivatives 0 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Restricted cash | Short-term Investments    
Assets:    
Investments, Fair Value Disclosure 15 20
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate debt securities | Short-term Investments    
Assets:    
Investments, Fair Value Disclosure 0 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate debt securities | Long-term Investments    
Assets:    
Investments, Fair Value Disclosure 0 0
Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Government and agency securities | Short-term Investments    
Assets:    
Investments, Fair Value Disclosure 0  
Recurring | Significant Other Observable Inputs (Level 2)    
Assets:    
Cash and cash equivalents 35 0
Derivatives   28
Total financial assets 6,991 9,197
Recurring | Significant Other Observable Inputs (Level 2) | Short-term Investments    
Assets:    
Investments, Fair Value Disclosure 2,737 3,723
Recurring | Significant Other Observable Inputs (Level 2) | Other Current Assets    
Assets:    
Derivatives 87  
Recurring | Significant Other Observable Inputs (Level 2) | Long-term Investments    
Assets:    
Investments, Fair Value Disclosure 4,132 5,446
Recurring | Significant Other Observable Inputs (Level 2) | Other Current Liabilities    
Liabilities:    
Derivatives 55 29
Recurring | Significant Other Observable Inputs (Level 2) | Restricted cash | Short-term Investments    
Assets:    
Investments, Fair Value Disclosure 0 0
Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt securities | Short-term Investments    
Assets:    
Investments, Fair Value Disclosure 2,696 3,723
Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt securities | Long-term Investments    
Assets:    
Investments, Fair Value Disclosure 4,132 $ 5,446
Recurring | Significant Other Observable Inputs (Level 2) | Government and agency securities | Short-term Investments    
Assets:    
Investments, Fair Value Disclosure 41  
Recurring | Significant Unobservable Inputs (Level 3)    
Assets:    
Cash and cash equivalents 0  
Total financial assets 276  
Recurring | Significant Unobservable Inputs (Level 3) | Short-term Investments    
Assets:    
Investments, Fair Value Disclosure 0  
Recurring | Significant Unobservable Inputs (Level 3) | Other Current Assets    
Assets:    
Derivatives 276  
Recurring | Significant Unobservable Inputs (Level 3) | Long-term Investments    
Assets:    
Investments, Fair Value Disclosure 0  
Recurring | Significant Unobservable Inputs (Level 3) | Other Current Liabilities    
Liabilities:    
Derivatives 0  
Recurring | Significant Unobservable Inputs (Level 3) | Restricted cash | Short-term Investments    
Assets:    
Investments, Fair Value Disclosure 0  
Recurring | Significant Unobservable Inputs (Level 3) | Corporate debt securities | Short-term Investments    
Assets:    
Investments, Fair Value Disclosure 0  
Recurring | Significant Unobservable Inputs (Level 3) | Corporate debt securities | Long-term Investments    
Assets:    
Investments, Fair Value Disclosure 0  
Recurring | Significant Unobservable Inputs (Level 3) | Government and agency securities | Short-term Investments    
Assets:    
Investments, Fair Value Disclosure $ 0