Stock-Based Compensation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended			6 Months Ended
	Apr. 30, 2016	Jan. 31, 2016	Apr. 30, 2015	Apr. 30, 2016	Apr. 30, 2015
Stock-Based Compensation
Pre-tax Stock-based compensation expense		$ 2
Stock-based compensation expense	$ 40		$ 59	$ 101	$ 110
Income tax benefit	(13)		(16)	(35)	(32)
Stock-based compensation expense, net of tax	$ 27		$ 43	$ 66	$ 78
Shares
Outstanding at beginning of period (in shares)		36,278		36,278
Weighted-Average Exercise Price
Outstanding at beginning of period (in dollars per share)		$ 26		$ 26
Restricted Stock Awards
Shares
Outstanding at beginning of period (in shares)		29,717		29,717
Granted (in shares)				27,334
Vested (in shares)				(2,137)
Cancelled Awards (in shares)				(23,926)
Forfeited (in shares)				(933)
Outstanding at end of period (in shares)	30,055			30,055
Weighted-Average Grant Date Fair Value Per Share
Outstanding at beginning of period (in dollars per share)		$ 32		$ 32
Granted (in dollars per share)				9
Vested (in dollars per share)				12
Cancelled Awards (in dollars per share)				32
Forfeited (in dollars per share)				13
Outstanding at end of period (in dollars per share)	$ 13			$ 13
Unrecognized pre-tax stock-based compensation expense and recognition period
Unrecognized pre-tax stock-based compensation expense	$ 238			$ 238
Remaining weighted-average vesting period over which pre-tax stock-based compensation expense is expected to be recognized				1 year 6 months
Stock Options
Unrecognized pre-tax stock-based compensation expense and recognition period
Unrecognized pre-tax stock-based compensation expense	$ 27			$ 27
Remaining weighted-average vesting period over which pre-tax stock-based compensation expense is expected to be recognized				2 years 2 months 12 days
Weighted-average fair value and the assumptions used to measure fair value
Weighted-average fair value	$ 2		$ 7	$ 4	$ 8
Expected volatility (as a percent)	31.60%		27.70%	36.40%	26.30%
Risk-free interest rate (as a percent)	1.60%		1.40%	1.90%	1.70%
Expected dividend yield (as a percent)	5.10%		2.20%	3.40%	1.70%
Expected term in years	5 years		5 years 2 months 12 days	6 years	5 years 9 months 18 days
Shares
Granted (in shares)				25,108
Exercised (in shares)				(1,371)
Cancelled Awards (in shares)				(26,252)
Forfeited and expired (in shares)				(1,689)
Outstanding at end of period (in shares)	32,074			32,074
Vested and expected to vest at end of period (in shares)	30,107			30,107
Exercisable at end of period (in shares)	17,966			17,966
Weighted-Average Exercise Price
Granted (in dollars per share)				$ 6
Exercised (in dollars per share)				7
Cancelled Awards (in dollars per share)				26
Forfeited and expired (in dollars per share)				16
Outstanding at end of period (in dollars per share)	$ 12			12
Vested and expected to vest at end of period (in dollars per share)	12			12
Exercisable at end of period (in dollars per share)	$ 11			$ 11
Weighted-Average Remaining Contractual Term
Outstanding at end of period				5 years 1 month 6 days
Vested and expected to vest at end of period				5 years
Exercisable at end of period				3 years 8 months 12 days
Aggregate Intrinsic Value
Outstanding at end of period	$ 47			$ 47
Vested and expected to vest at end of period	47			47
Exercisable at end of period	47			47
Options exercised	$ 5			$ 7
Performance-Based restricted stock units
Stock-Based Compensation
Expected performance period in years				2 years 10 months 24 days	2 years 10 months 24 days
Weighted-average fair value and the assumptions used to measure fair value
Weighted-average fair value				$ 13	$ 47
Expected volatility (as a percent)				32.50%	33.60%
Risk-free interest rate (as a percent)				1.20%	1.00%