Stockholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions			3 Months Ended		12 Months Ended
	Feb. 22, 2018	Feb. 21, 2018	Jan. 31, 2018	Jan. 31, 2017	Oct. 31, 2017
Equity, Class of Treasury Stock [Line Items]
Cash dividends declared per share, quarterly (in dollars per share)			$ 0.15	$ 0.13
Share Repurchase program
Equity, Class of Treasury Stock [Line Items]
Common stock retired (in shares)			1.9		1.7
Repurchases of common stock recorded as a reduction to stockholders' equity			$ 750
Share repurchase authorization remaining			$ 5,000
ASR Agreement
Equity, Class of Treasury Stock [Line Items]
Common stock retired (in shares)			50.0
Subsequent Event
Equity, Class of Treasury Stock [Line Items]
Cash dividends declared per share, quarterly (in dollars per share)	$ 0.1125	$ 0.075
Subsequent Event | Share Repurchase program
Equity, Class of Treasury Stock [Line Items]
Share repurchase program additional authorized amount		$ 2,500