Fair Value Measurements - Recurring Basis (Details) - Recurring - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	$ 9,232	$ 8,543
Total liabilities at fair value	(8)	(26)
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	9,220	8,543
Total liabilities at fair value	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	12	0
Total liabilities at fair value	(8)	(26)
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	0	0
Total liabilities at fair value	0	0
Cash and cash equivalents | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	8,968	8,345
Cash and cash equivalents | Foreign government treasury bills
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	25	34
Cash and cash equivalents | Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	8,968	8,345
Cash and cash equivalents | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign government treasury bills
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	25	34
Cash and cash equivalents | Significant Other Observable Inputs (Level 2) | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	0	0
Cash and cash equivalents | Significant Other Observable Inputs (Level 2) | Foreign government treasury bills
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	0	0
Cash and cash equivalents | Significant Unobservable Inputs (Level 3) | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	0	0
Cash and cash equivalents | Significant Unobservable Inputs (Level 3) | Foreign government treasury bills
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	0	0
Other current assets | U.S. treasuries and government agency securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	227	164
Other current assets | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. treasuries and government agency securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	227	164
Other current assets | Significant Other Observable Inputs (Level 2) | U.S. treasuries and government agency securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	0	0
Other current assets | Significant Unobservable Inputs (Level 3) | U.S. treasuries and government agency securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	0	0
Other assets | Foreign currency forward contracts | Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	12
Other assets | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign currency forward contracts | Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	0
Other assets | Significant Other Observable Inputs (Level 2) | Foreign currency forward contracts | Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	12
Other assets | Significant Unobservable Inputs (Level 3) | Foreign currency forward contracts | Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets at fair value	0
Accrued expenses and other liabilities | Foreign currency forward contracts | Not Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total liabilities at fair value	(1)	(2)
Accrued expenses and other liabilities | Foreign currency forward contracts | Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total liabilities at fair value	(7)	(24)
Accrued expenses and other liabilities | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign currency forward contracts | Not Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total liabilities at fair value	0	0
Accrued expenses and other liabilities | Quoted Prices in Active Markets for Identical Assets (Level 1) | Foreign currency forward contracts | Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total liabilities at fair value	0	0
Accrued expenses and other liabilities | Significant Other Observable Inputs (Level 2) | Foreign currency forward contracts | Not Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total liabilities at fair value	(1)	(2)
Accrued expenses and other liabilities | Significant Other Observable Inputs (Level 2) | Foreign currency forward contracts | Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total liabilities at fair value	(7)	(24)
Accrued expenses and other liabilities | Significant Unobservable Inputs (Level 3) | Foreign currency forward contracts | Not Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total liabilities at fair value	0	0
Accrued expenses and other liabilities | Significant Unobservable Inputs (Level 3) | Foreign currency forward contracts | Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total liabilities at fair value	$ 0	$ 0