Investments - Gains (Losses) on Strategic Investments, Net (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2020	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2020	Jul. 31, 2019
Investment Holdings [Line Items]
Net unrealized gains (loss) recognized		$ (633)		$ (586)
Gains on strategic investments, net		682	$ 109	874	$ 390
Publicly traded securities
Investment Holdings [Line Items]
Net unrealized gains (loss) recognized	$ 617	623	66	623	216
Privately held securities
Investment Holdings [Line Items]
Net unrealized gains (loss) recognized		14	0	(24)	122
Equity securities
Investment Holdings [Line Items]
Net realized gains (losses) recognized		49	43	288	62
Debt securities
Investment Holdings [Line Items]
Net realized gains (losses) recognized		$ (4)	$ 0	$ (13)	$ (10)