Summary of Significant Accounting Policies - Variable Interest Entities (Details) - USD ($) $ in Millions	Apr. 30, 2020	Jan. 31, 2020	Oct. 31, 2019
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	$ 6,440	$ 6,440	$ 6,917
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	10,296		10,640
Cash and cash equivalents	1,547		1,370
Financial Services Operations
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets		$ 2,081	2,774
Variable Interest Entity, Primary Beneficiary [Member] | Variable Interest Entity Primary Beneficiary, Blue Diamond Parts [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	18		32
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	4
Cash and cash equivalents	4		2
Variable Interest Entity, Primary Beneficiary [Member] | Variable Interest Entity Primary Beneficiary Securitizations Treated As Borrowings [Member] | Financial Services Operations
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	806		927
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	725		838
Variable Interest Entity, Primary Beneficiary [Member] | Transaction Does Not Qualify for Sale Accounting [Member] | Financial Services Operations
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	255		537
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	$ 180		$ 279