Fair Value Measurements and Investments - Schedule of Gains and Losses on Marketable and Non-Marketable Equity Securities (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Net gain (loss) on equity securities sold during the period	$ 1	$ 15	$ 5	$ 15
Unrealized gain (loss) on equity securities held as of the end of the period	(23)	79	(9)	59
Total gain (loss) recognized in non-operating income (expense), net	$ (22)	$ 94	$ (4)	$ 74

Amount of unrealized and realized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117546-209714

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

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

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