Retirement and Post-Retirement Benefit Plans - Defined Contribution Plans (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2018
Retirement Benefits [Abstract]
Total defined contribution expense	$ 108	$ 107	$ 110
Defined Contribution Plan Disclosure [Line Items]
Employee service period	3 years
HP 401(k) Plan
Defined Contribution Plan Disclosure [Line Items]
Employer matching contributions, as a percent	100.00%
Percentage of maximum matching contribution	4.00%