Taxes on Earnings - Uncertain Tax Positions (Narrative) (Details) $ in Millions	12 Months Ended
	Oct. 31, 2020 USD ($) country	Oct. 31, 2019 USD ($)	Oct. 31, 2018 USD ($)	Oct. 31, 2017 USD ($)
Income Tax Disclosure [Abstract]
Unrecognized tax benefits	$ 820	$ 929	$ 7,771	$ 10,808
Unrecognized tax benefits that would affect effective tax rate if realized	657	803
Decrease in unrecognized tax benefits	109
Accrued income tax for interest and penalties	$ 34	$ 56	$ 160
Likelihood of no resolution period	12 months
Number of other countries in which HP is subject to income taxes | country	60
Reasonably possible decrease in existing unrecognized tax benefits within the next 12 months	$ 107
Undistributed earnings from non-U.S. operations	$ 5,700