Stockholders' Deficit - Narrative (Details) - USD ($)		3 Months Ended		6 Months Ended
	Feb. 20, 2020	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2020	Apr. 30, 2019	Feb. 22, 2020	Oct. 31, 2019
Stockholders' Equity Note [Abstract]
Repurchases of common stock (shares)		4,000,000	34,000,000	39,000,000	66,000,000
Payment in connection with repurchases of shares		$ 100,000,000	$ 700,000,000	$ 814,000,000	$ 1,411,000,000
Subsequent Event [Line Items]
Authorized repurchase amount						$ 15,000,000,000.0
Share repurchase authorization remaining		$ 15,000,000,000.0		$ 15,000,000,000.0
Common stock dividends, preferred share purchase right declared (in shares)	1
Preferred stock, par value (usd per share)		$ 0.01		$ 0.01			$ 0.01
Exercise price per right (usd per share)	$ 100
Common stock ownership percentage required to purchase additional shares	20.00%
Maximum common stock ownership percentage that can be acquired for rights to be exchangeable	50.00%
Redemption price per right (usd per share)	$ 0.01
Preferred stock, shares authorized (in shares)		300,000,000		300,000,000			300,000,000
Preferred stock, shares issued (in shares)		0		0			0
Series A Junior Participating Preferred Stock
Subsequent Event [Line Items]
Number of preferred stock called by each right (in shares)	0.01
Preferred stock, par value (usd per share)	$ 0.01	$ 0.01		$ 0.01
Preferred stock, shares authorized (in shares)		50,000,000		50,000,000
Preferred stock, shares issued (in shares)		0		0
Preferred stock, shares outstanding (in shares)		0		0
Common Stock
Subsequent Event [Line Items]
Number of shares exchanged for each outstanding right (in shares)	1