Retirement and Post-Retirement Benefit Plans - Defined Contribution Plans (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2017
Retirement Benefits [Abstract]
Total defined contribution expense	$ 107	$ 110	$ 103
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%