Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Short-term investments	$ 4,417	$ 5,789
Short-term investments expected to mature in one year or less	$ 3,700

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

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-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
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