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