Segment Information - Segment Operating Results from Continuing Operations (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Oct. 31, 2020	Jul. 31, 2020	Apr. 30, 2020	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2018
Segment Reporting Information
Net revenue	$ 7,208	$ 6,816	$ 6,009	$ 6,949	$ 7,215	$ 7,217	$ 7,150	$ 7,553	$ 26,982	$ 29,135	$ 30,852
Segment earnings (loss) from operations	$ 145	$ 12	$ (834)	$ 348	$ 460	$ (76)	$ 434	$ 456	(329)	1,274	1,737
Elimination of intersegment net revenue
Segment Reporting Information
Net revenue									(598)	(615)	(780)
Operating segments
Segment Reporting Information
Net revenue									27,580	29,750	31,632
Segment earnings (loss) from operations									2,303	3,096	2,975
Compute
Segment Reporting Information
Net revenue									11,821	13,250	14,616
Compute | Elimination of intersegment net revenue
Segment Reporting Information
Net revenue									(394)	(392)	(526)
Compute | Operating segments
Segment Reporting Information
Net revenue									12,215	13,642	15,142
Segment earnings (loss) from operations									893	1,550	1,306
HPC & MCS
Segment Reporting Information
Net revenue									2,965	2,786	2,875
HPC & MCS | Elimination of intersegment net revenue
Segment Reporting Information
Net revenue									(71)	(124)	(112)
HPC & MCS | Operating segments
Segment Reporting Information
Net revenue									3,036	2,910	2,987
Segment earnings (loss) from operations									237	320	384
Storage
Segment Reporting Information
Net revenue									4,583	5,114	5,054
Storage | Elimination of intersegment net revenue
Segment Reporting Information
Net revenue									(98)	(71)	(104)
Storage | Operating segments
Segment Reporting Information
Net revenue									4,681	5,185	5,158
Segment earnings (loss) from operations									719	924	830
A & PS
Segment Reporting Information
Net revenue									946	1,004	1,111
A & PS | Elimination of intersegment net revenue
Segment Reporting Information
Net revenue									(5)	(8)	(7)
A & PS | Operating segments
Segment Reporting Information
Net revenue									951	1,012	1,118
Segment earnings (loss) from operations									(5)	(54)	(79)
Intelligent Edge
Segment Reporting Information
Net revenue									2,837	2,904	2,997
Intelligent Edge | Elimination of intersegment net revenue
Segment Reporting Information
Net revenue									(18)	(9)	(16)
Intelligent Edge | Operating segments
Segment Reporting Information
Net revenue									2,855	2,913	3,013
Segment earnings (loss) from operations									281	159	339
Financial Services
Segment Reporting Information
Net revenue									3,340	3,570	3,656
Financial Services | Elimination of intersegment net revenue
Segment Reporting Information
Net revenue									(12)	(11)	(15)
Financial Services | Operating segments
Segment Reporting Information
Net revenue									3,352	3,581	3,671
Segment earnings (loss) from operations									278	305	286
Corporate Investments
Segment Reporting Information
Net revenue									490	507	543
Corporate Investments | Elimination of intersegment net revenue
Segment Reporting Information
Net revenue									0	0	0
Corporate Investments | Operating segments
Segment Reporting Information
Net revenue									490	507	543
Segment earnings (loss) from operations									$ (100)	$ (108)	$ (91)