Discontinued Operations - Schedule of Discontinued Operations, Financial Results (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net loss from discontinued operations	$ 15	$ (1)	$ (72)	$ (46)	$ 146	$ (120)	$ (134)	$ 16	$ (104)	$ (92)	$ (76)
Everett SpinCo, Inc. and Seattle SpinCo, Inc. | Spinoff
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net revenue									0	8,511	19,843
Cost of revenue									0	5,890	15,000
Expenses									51	3,063	4,596
Interest and other, net									58	39	28
(Loss) earnings from discontinued operations before taxes									(109)	(481)	219
Benefit (provision) for taxes									5	389	(295)
Net loss from discontinued operations									$ (104)	$ (92)	$ (76)