Fair Value Measurement of Assets and Liabilities - Financial Assets and Liabilities Measured at Fair Value, Recurring (Details) - Recurring - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Assets:
Cash and cash equivalents	$ 1,006	$ 923
Total financial assets	6,518	4,081
Short-term investments
Assets:
Investments	4,297	1,850
Derivatives
Assets:
Derivatives	681	347
Long-term Investments
Assets:
Investments	534	961
Derivatives
Liabilities:
Derivatives	31	23
Restricted cash | Short-term investments
Assets:
Investments	19	21
Corporate debt securities | Short-term investments
Assets:
Investments	3,869	1,654
Corporate debt securities | Long-term Investments
Assets:
Investments	534	961
Government and agency securities | Short-term investments
Assets:
Investments	409	175
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	906	923
Total financial assets	925	944
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments
Assets:
Investments	19	21
Quoted Prices in Active Markets for Identical Assets (Level 1) | Derivatives
Assets:
Derivatives	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Long-term Investments
Assets:
Investments	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Derivatives
Liabilities:
Derivatives	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Restricted cash | Short-term investments
Assets:
Investments	19	21
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate debt securities | Short-term investments
Assets:
Investments	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate debt securities | Long-term Investments
Assets:
Investments	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Government and agency securities | Short-term investments
Assets:
Investments	0	0
Significant Other Observable Inputs (Level 2)
Assets:
Cash and cash equivalents	100	0
Total financial assets	5,007	2,856
Significant Other Observable Inputs (Level 2) | Short-term investments
Assets:
Investments	4,278	1,829
Significant Other Observable Inputs (Level 2) | Derivatives
Assets:
Derivatives	95	66
Significant Other Observable Inputs (Level 2) | Long-term Investments
Assets:
Investments	534	961
Significant Other Observable Inputs (Level 2) | Derivatives
Liabilities:
Derivatives	31	23
Significant Other Observable Inputs (Level 2) | Restricted cash | Short-term investments
Assets:
Investments	0	0
Significant Other Observable Inputs (Level 2) | Corporate debt securities | Short-term investments
Assets:
Investments	3,869	1,654
Significant Other Observable Inputs (Level 2) | Corporate debt securities | Long-term Investments
Assets:
Investments	534	961
Significant Other Observable Inputs (Level 2) | Government and agency securities | Short-term investments
Assets:
Investments	409	175
Significant Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	0	0
Total financial assets	586	281
Significant Unobservable Inputs (Level 3) | Short-term investments
Assets:
Investments	0	0
Significant Unobservable Inputs (Level 3) | Derivatives
Assets:
Derivatives	586	281
Significant Unobservable Inputs (Level 3) | Long-term Investments
Assets:
Investments	0	0
Significant Unobservable Inputs (Level 3) | Derivatives
Liabilities:
Derivatives	0	0
Significant Unobservable Inputs (Level 3) | Restricted cash | Short-term investments
Assets:
Investments	0	0
Significant Unobservable Inputs (Level 3) | Corporate debt securities | Short-term investments
Assets:
Investments	0	0
Significant Unobservable Inputs (Level 3) | Corporate debt securities | Long-term Investments
Assets:
Investments	0	0
Significant Unobservable Inputs (Level 3) | Government and agency securities | Short-term investments
Assets:
Investments	$ 0	$ 0