Restructuring (Details) $ in Millions	3 Months Ended								12 Months Ended
	Oct. 31, 2018 USD ($)	Jul. 31, 2018 USD ($)	Apr. 30, 2018 USD ($)	Jan. 31, 2018 USD ($)	Oct. 31, 2017 USD ($)	Jul. 31, 2017 USD ($)	Apr. 30, 2017 USD ($)	Jan. 31, 2017 USD ($)	Oct. 31, 2018 USD ($) position	Oct. 31, 2017 USD ($)	Oct. 31, 2016 USD ($)
Restructuring and related costs
Reversal of restructuring charges											$ 2
Restructuring Reserve
Charges	$ 5	$ 2	$ 9	$ 3	$ 113	$ 152	$ 69	$ 83	$ 19	$ 417	417
Short-term portion of restructuring reserve, recorded in Accrued restructuring	294				445				294	445
Long-term portion of restructuring reserve, recorded in Other liabilities	31				96				31	96
Restructuring Plan All
Restructuring Reserve
Balance at the beginning of the period				254				298	254	298	151
Charges									19	417	419
Cash payments									(181)	(412)	(288)
Non-cash items									(8)	(49)	16
Balance at the end of the period	84				254				84	254	298
Total costs incurred to date as of October 31, 2018	2,242								2,242
Total expected costs to be incurred as of October 31, 2018	2,242								2,242
Short-term portion of restructuring reserve, recorded in Accrued restructuring	53				158				53	158
Fiscal 2015 Plan
Restructuring Reserve
Total expected costs to be incurred as of October 31, 2018	800								$ 800
Expected positions to be eliminated | position									8,300
Fiscal 2015 Plan | Employee Severance
Restructuring Reserve
Balance at the beginning of the period				219				234	$ 219	234	67
Charges									9	374	301
Cash payments									(158)	(355)	(172)
Non-cash items									(8)	(34)	38
Balance at the end of the period	62				219				62	219	234
Total costs incurred to date as of October 31, 2018	751								751
Total expected costs to be incurred as of October 31, 2018	751								751
Fiscal 2015 Plan | Infrastructure and other
Restructuring Reserve
Balance at the beginning of the period				17				13	17	13	0
Charges									(2)	37	42
Cash payments									(8)	(19)	(19)
Non-cash items									3	(14)	(10)
Balance at the end of the period	10				17				10	17	13
Total costs incurred to date as of October 31, 2018	78								78
Total expected costs to be incurred as of October 31, 2018	78								78
Fiscal 2015 Plan | Real estate consolidation
Restructuring Reserve
Total expected costs to be incurred as of October 31, 2018	78								78
Fiscal 2012 Plan
Restructuring Reserve
Total costs incurred to date as of October 31, 2018	1,400								1,400
Fiscal 2012 Plan | Infrastructure and other
Restructuring Reserve
Balance at the beginning of the period				2				14	2	14	37
Charges									(1)	0	1
Cash payments									0	(6)	(15)
Non-cash items									0	(6)	(9)
Balance at the end of the period	1				2				1	2	14
Total costs incurred to date as of October 31, 2018	145								145
Total expected costs to be incurred as of October 31, 2018	145								145
Fiscal 2012 Plan | Employee Severance and EER
Restructuring Reserve
Balance at the beginning of the period				$ 16				$ 37	16	37	47
Charges									13	6	75
Cash payments									(15)	(32)	(82)
Non-cash items									(3)	5	(3)
Balance at the end of the period	11				$ 16				11	16	37
Total costs incurred to date as of October 31, 2018	1,268								1,268
Total expected costs to be incurred as of October 31, 2018	$ 1,268								$ 1,268
Expected positions to be eliminated | position									10,300
Discontinued Operations
Restructuring Reserve
Charges										$ 251	$ 819