Summary of Significant Accounting Policies - Recently Adopted Accounting Pronouncements (Details) - USD ($) $ in Millions	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liabilities	$ 1,179
Right-of-use assets from operating leases	1,107
Increase to accumulated deficit	$ 1,961	$ 818
Adjustment for adoption of accounting standards
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liabilities		1,200
Right-of-use assets from operating leases		$ 1,200
Increase to accumulated deficit			$ 212