Valuation of Debt and Equity Investments and Certain Liabilities - Investments at Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 3,107	$ 2,437
Short-term investments	3,461	2,950
Long-term investments	49	300
Measured at fair value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	2,482	1,991
Short-term investments	3,461	2,950
Long-term investments	18	272
Measured at fair value \| Available-for-sale debt securities \| Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	886	1,213
Short-term investments	0	0
Long-term investments	0	0
Measured at fair value \| Available-for-sale debt securities \| Corporate obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	256	174
Short-term investments	407	1,216
Long-term investments	0	0
Measured at fair value \| Available-for-sale debt securities \| U.S. government agency and Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	1,340	604
Short-term investments	3,054	1,734
Long-term investments	0	0
Measured at fair value \| Trading securities \| Mutual funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Short-term investments	0	0
Long-term investments	18	272
Other measurement basis \| Equity-method investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Short-term investments	0	0
Long-term investments	27	24
Other measurement basis \| Non-marketable equity investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Short-term investments	0	0
Long-term investments	4	4
Other measurement basis \| Cash on hand
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	625	446
Short-term investments	0	0
Long-term investments	$ 0	$ 0

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.

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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- Definition

Amount of investments including trading securities, available-for-sale securities, held-to-maturity securities, and short-term investments classified as other and current.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 942
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-Section S99
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
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-Section S99
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