Summary of significant accounting policies (Variable Interest Entities) (Details) (USD $) In Millions, unless otherwise specified	Jan. 31, 2012	Oct. 31, 2011
Variable Interest Entity Primary Beneficiary Blue Diamond Parts And Blue Diamond Truck [Member]
Variable Interest Entity [Line Items]
Assets	$ 225	$ 306
Liabilities	140	158
Cash and cash equivalents	15	38
Securitizations Treated as Borrowings [Member] | Financial Services [Member]
Variable Interest Entity [Line Items]
Assets	1,500	1,800
Liabilities	1,300	1,500
Transaction Does Not Qualify for Sale Accounting [Member] | Financial Services [Member]
Variable Interest Entity [Line Items]
Assets	394	468
Liabilities	$ 166	$ 216