Stock-Based Compensation - Restricted Stock Units (Narrative) (Details) - Restricted Stock Units - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares assumed through acquisition (in shares)			8
Weighted- average grant date fair value of shares assumed (in dollars per share)			$ 33
Total grant date fair value of restricted stock awards vested	$ 162	$ 54	$ 889
Unrecognized pre-tax stock-based compensation expense related to non-vested restricted stock awards	$ 205
Remaining weighted-average vesting period	1 year 3 months 18 days