Restructuring and Impairments - Narrative (Details) - USD ($) $ in Millions	3 Months Ended								9 Months Ended	12 Months Ended
	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Jan. 31, 2017	Oct. 31, 2015	Jul. 31, 2015	Jul. 31, 2014	Jan. 31, 2014	Jul. 31, 2018	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2016	Jul. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring charges										$ (1)	$ 3	$ 10
Liability, Defined Benefit Plan, Noncurrent		$ 2,497								2,097	2,497
Restructuring and Related Cost, Incurred Cost										3	22	4
Asset impairment charges										14	13	27
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)										0	0	1
Pension Liability			$ 23
Restructuring Benefit			8
Inventory Reserve Charge			10
Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost										0	0	0
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges					$ 10	$ 13
Restructuring and Related Cost, Incurred Cost										3	22	4
Lease Vacancy [Member] [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost										0	0	0
North America Truck [Member]
Restructuring Cost and Reserve [Line Items]
Asset impairment charges												17
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)												8
Navistar Financial Corporation [Member]
Restructuring Cost and Reserve [Line Items]
Asset impairment charges									$ 1
Melrose Park [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 2		41
Global Operations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges		6								1
Huntsville Engine Plant [Member] | North America Truck [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges								$ 23
Brazilian Reporting Unit [Member]
Restructuring Cost and Reserve [Line Items]
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)												$ 1
Indefinite-Lived Intangible Assets (Excluding Goodwill)													$ 1
Other Postretirement Benefits Plan [Member]
Restructuring Cost and Reserve [Line Items]
Liability, Defined Benefit Plan, Noncurrent		$ 1,061								$ 914	$ 1,061
Other Postretirement Benefits Plan [Member] | Chatham [Member] | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Postemployment Benefits, Period Expense				$ 6			$ 14
Liability, Defined Benefit Plan, Noncurrent			$ 66
Voluntary Separation Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges					$ 37
Cherokee [Domain]
Restructuring Cost and Reserve [Line Items]
Asset impairment charges									$ 2