Fair Value Measurement of Assets and Liabilities - Financial Assets and Liabilities Measured at Fair Value, Recurring (Details) - Recurring - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Assets:
Cash and cash equivalents	$ 963	$ 901
Total financial assets	4,887	4,057
Short-term investments
Assets:
Investments	2,697	1,850
Derivatives
Assets:
Derivatives	836	345
Long-term Investments
Assets:
Investments	391	961
Derivatives
Liabilities:
Derivatives	29	20
Restricted cash | Short-term investments
Assets:
Investments	126	21
Corporate debt securities | Short-term investments
Assets:
Investments	2,571	1,654
Corporate debt securities | Long-term Investments
Assets:
Investments	391	961
Government and agency securities | Short-term investments
Assets:
Investments		175
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	933	901
Total financial assets	1,059	922
Quoted Prices in Active Markets for Identical Assets (Level 1) | Short-term investments
Assets:
Investments	126	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	126	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
Significant Other Observable Inputs (Level 2)
Assets:
Cash and cash equivalents	30	0
Total financial assets	3,051	2,854
Significant Other Observable Inputs (Level 2) | Short-term investments
Assets:
Investments	2,571	1,829
Significant Other Observable Inputs (Level 2) | Derivatives
Assets:
Derivatives	59	64
Significant Other Observable Inputs (Level 2) | Long-term Investments
Assets:
Investments	391	961
Significant Other Observable Inputs (Level 2) | Derivatives
Liabilities:
Derivatives	29	20
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	2,571	1,654
Significant Other Observable Inputs (Level 2) | Corporate debt securities | Long-term Investments
Assets:
Investments	391	961
Significant Other Observable Inputs (Level 2) | Government and agency securities | Short-term investments
Assets:
Investments		175
Significant Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	0	0
Total financial assets	777	281
Significant Unobservable Inputs (Level 3) | Short-term investments
Assets:
Investments	0	0
Significant Unobservable Inputs (Level 3) | Derivatives
Assets:
Derivatives	777	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