Postretirement benefits (Components of Net Periodic Benefit Expense (Income)) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jan. 31, 2012	Jan. 31, 2011
Pension Benefit [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost for benefits earned during the period	$ 4	$ 4
Interest on obligations	43	47
Amortization of cumulative loss	28	25
Amortization of prior service benefit	0	0
Curtailments	0	2
Contractual termination benefits	0	3
Expected return on assets	(48)	(52)
Net postretirement benefits expense (income)	27	29
Health and Life Insurance Benefits [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost for benefits earned during the period	1	2
Interest on obligations	21	13
Amortization of cumulative loss	9	0
Amortization of prior service benefit	(1)	(8)
Curtailments	0	0
Contractual termination benefits	(2)	0
Expected return on assets	(9)	(10)
Net postretirement benefits expense (income)	$ 19	$ (3)