Fair Value Measurements and Investments - Schedule of Gains and Losses on Marketable and Non-Marketable Equity Securities (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2020 |
Jun. 30, 2019 |
Jun. 30, 2020 |
Jun. 30, 2019 |
|
| Fair Value Disclosures [Abstract] | ||||
| Net gain (loss) on equity securities sold during the period | $ 0 | $ 1 | $ 5 | $ 16 |
| Unrealized gain (loss) on equity securities held as of the end of the period | 68 | 10 | 59 | 69 |
| Total gain (loss) recognized in non-operating income (expense), net | $ 68 | $ 11 | $ 64 | $ 85 |