Fair Value Measurement of Assets and Liabilities - Financial Assets and Liabilities Measured at Fair Value, Recurring (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Assets:
Equity investment in Adevinta	$ 10,354	$ 0
Recurring
Assets:
Cash and cash equivalents	2,128	1,101
Equity investment in Adevinta	10,354
Derivatives	1,180	1,113
Total financial assets	19,145	4,892
Liabilities:
Derivatives	26	44
Recurring \| Short-term investments
Assets:
Investments	4,738	2,392
Recurring \| Long-term Investments
Assets:
Investments	745	286
Recurring \| Restricted cash \| Short-term investments
Assets:
Investments	15	137
Recurring \| Corporate debt securities \| Short-term investments
Assets:
Investments	4,598	2,255
Recurring \| Corporate debt securities \| Long-term Investments
Assets:
Investments	636	286
Recurring \| Government and agency securities \| Short-term investments
Assets:
Investments	125
Recurring \| Government and agency securities \| Long-term Investments
Assets:
Investments	109
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	2,128	890
Equity investment in Adevinta	10,354
Derivatives	0	0
Total financial assets	12,497	1,027
Liabilities:
Derivatives	0	0
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Short-term investments
Assets:
Investments	15	137
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Long-term Investments
Assets:
Investments	0	0
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Restricted cash \| Short-term investments
Assets:
Investments	15	137
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Corporate debt securities \| Short-term investments
Assets:
Investments	0	0
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Corporate debt securities \| Long-term Investments
Assets:
Investments	0	0
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Government and agency securities \| Short-term investments
Assets:
Investments	0
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Government and agency securities \| Long-term Investments
Assets:
Investments	0
Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Cash and cash equivalents	0	211
Equity investment in Adevinta	0
Derivatives	57	62
Total financial assets	5,525	2,814
Liabilities:
Derivatives	26	44
Recurring \| Significant Other Observable Inputs (Level 2) \| Short-term investments
Assets:
Investments	4,723	2,255
Recurring \| Significant Other Observable Inputs (Level 2) \| Long-term Investments
Assets:
Investments	745	286
Recurring \| Significant Other Observable Inputs (Level 2) \| Restricted cash \| Short-term investments
Assets:
Investments	0	0
Recurring \| Significant Other Observable Inputs (Level 2) \| Corporate debt securities \| Short-term investments
Assets:
Investments	4,598	2,255
Recurring \| Significant Other Observable Inputs (Level 2) \| Corporate debt securities \| Long-term Investments
Assets:
Investments	636	286
Recurring \| Significant Other Observable Inputs (Level 2) \| Government and agency securities \| Short-term investments
Assets:
Investments	125
Recurring \| Significant Other Observable Inputs (Level 2) \| Government and agency securities \| Long-term Investments
Assets:
Investments	109
Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	0	0
Equity investment in Adevinta	0
Derivatives	1,123	1,051
Total financial assets	1,123	1,051
Liabilities:
Derivatives	0	0
Recurring \| Significant Unobservable Inputs (Level 3) \| Short-term investments
Assets:
Investments	0	0
Recurring \| Significant Unobservable Inputs (Level 3) \| Long-term Investments
Assets:
Investments	0	0
Recurring \| Significant Unobservable Inputs (Level 3) \| Restricted cash \| Short-term investments
Assets:
Investments	0	0
Recurring \| Significant Unobservable Inputs (Level 3) \| Corporate debt securities \| Short-term investments
Assets:
Investments	0	0
Recurring \| Significant Unobservable Inputs (Level 3) \| Corporate debt securities \| Long-term Investments
Assets:
Investments	0	$ 0
Recurring \| Significant Unobservable Inputs (Level 3) \| Government and agency securities \| Short-term investments
Assets:
Investments	0
Recurring \| Significant Unobservable Inputs (Level 3) \| Government and agency securities \| Long-term Investments
Assets:
Investments	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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