Stockholders' Equity (Details 2) - USD ($) $ / shares in Units, shares in Millions			3 Months Ended								12 Months Ended
	Feb. 22, 2018	Feb. 21, 2018	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2016	Oct. 16, 2017	May 24, 2016	Oct. 13, 2015
Components of accumulated other comprehensive income, net of taxes
Balance at beginning of period						$ (2,895,000,000)					$ (2,895,000,000)
Balance at end of period			$ (3,218,000,000)				$ (2,895,000,000)				$ (3,218,000,000)	$ (2,895,000,000)
Dividends
Cash dividends declared per share (in dollars per share)	$ 0.1125	$ 0.075	$ 0.1125	$ 0.1125	$ 0.1125	$ 0.15	$ 0	$ 0.065	$ 0.065	$ 0.13	$ 0.4875	$ 0.26	$ 0.22
Stock Repurchase Program
Stock repurchase program authorized amount																$ 3,000,000,000.00
Remaining authorization			$ 4,700,000,000								$ 4,700,000,000
Share Repurchase Program
Stock Repurchase Program
Stock repurchase program authorized amount		$ 2,500,000,000.0												$ 5,000,000,000.0	$ 3,000,000,000.0
Retired (shares)											222.0	136.0
Open market repurchases (shares)											2.4	1.7
Open market repurchases												$ 24,000,000
Accelerated Share Repurchase Agreement
Stock Repurchase Program
Repurchased											$ 3,600,000,000	2,600,000,000
Net unrealized gains (losses) on available-for-sale securities
Components of accumulated other comprehensive income, net of taxes
Balance at beginning of period						$ 29,000,000					29,000,000
Release of cumulative translation adjustment as a result of divestitures											0
Other comprehensive (loss) income before reclassifications											(3,000,000)	(10,000,000)	$ (2,000,000)
Reclassifications of (gains) losses into earnings											(9,000,000)
Balance at end of period			17,000,000				$ 29,000,000				17,000,000	29,000,000
Net unrealized gains (losses) on cash flow hedges
Components of accumulated other comprehensive income, net of taxes
Balance at beginning of period						(48,000,000)					(48,000,000)
Release of cumulative translation adjustment as a result of divestitures											0
Other comprehensive (loss) income before reclassifications											147,000,000	52,000,000	$ 212,000,000
Reclassifications of (gains) losses into earnings											7,000,000
Balance at end of period			106,000,000				(48,000,000)				106,000,000	(48,000,000)
Unrealized components of defined benefit plans
Components of accumulated other comprehensive income, net of taxes
Balance at beginning of period						(2,690,000,000)					(2,690,000,000)
Release of cumulative translation adjustment as a result of divestitures											0
Other comprehensive (loss) income before reclassifications											(421,000,000)
Reclassifications of (gains) losses into earnings											189,000,000
Balance at end of period			(2,922,000,000)				(2,690,000,000)				(2,922,000,000)	(2,690,000,000)
Cumulative translation adjustment
Components of accumulated other comprehensive income, net of taxes
Balance at beginning of period						(186,000,000)					(186,000,000)
Release of cumulative translation adjustment as a result of divestitures											(186,000,000)
Other comprehensive (loss) income before reclassifications											(67,000,000)
Reclassifications of (gains) losses into earnings											20,000,000
Balance at end of period			(419,000,000)				(186,000,000)				(419,000,000)	(186,000,000)
Accumulated Other Comprehensive Loss
Components of accumulated other comprehensive income, net of taxes
Balance at beginning of period						$ (2,895,000,000)					(2,895,000,000)
Release of cumulative translation adjustment as a result of divestitures											(186,000,000)
Other comprehensive (loss) income before reclassifications											(344,000,000)
Reclassifications of (gains) losses into earnings											207,000,000
Balance at end of period			$ (3,218,000,000)				$ (2,895,000,000)				$ (3,218,000,000)	$ (2,895,000,000)