Stockholders' Deficit - Narrative (Details) - USD ($) shares in Millions, $ in Millions		3 Months Ended		6 Months Ended
	Jun. 19, 2018	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2019	Apr. 30, 2018	Jan. 31, 2019
Stockholders' Equity Note [Abstract]
Repurchases of common stock (shares)		34	35	66	56
Payment in connection with repurchases of shares		$ 700	$ 800	$ 1,411	$ 1,263
Share repurchase increase in authorization	$ 4,000
Remaining shares authorized for repurchase (shares)						$ 2,500