Allowance for doubtful accounts (Rollforward) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended					6 Months Ended	9 Months Ended
	Jul. 31, 2012 segments		Jul. 31, 2011		Apr. 30, 2011	Apr. 30, 2011	Jul. 31, 2012		Jul. 31, 2011
Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Start of Period	$ 45		$ 76			$ 96	$ 50		$ 96
Provision for doubtful accounts, net of recoveries	1		(3)				1		(5)
Charge-off of accounts	(3)	[1]	(6)	[1]			(8)	[1]	(24)	[1]
Financing Receivable, Allowance for Credit Losses, End of Period	43		67		76	76	43		67
Number of portfolio segments of finance receivables	2
Losses recognized at time of repossession	1				2	17	4
Retail [Member]
Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Start of Period	26		40			58	31		58
Provision for doubtful accounts, net of recoveries	1		(1)				(1)		(1)
Charge-off of accounts	(1)	[1]	(2)	[1]			(4)	[1]	(20)	[1]
Financing Receivable, Allowance for Credit Losses, End of Period	26		37				26		37
Wholesale [Member]
Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Start of Period	2		2			2	2		2
Provision for doubtful accounts, net of recoveries	0		0				0		0
Charge-off of accounts	0	[1]	0	[1]			0	[1]	0	[1]
Financing Receivable, Allowance for Credit Losses, End of Period	2		2				2		2
Number of classes of receivables in each portfolio	1
Trade and Other Receivables [Member]
Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance for Credit Losses, Start of Period	17		34			36	17		36
Provision for doubtful accounts, net of recoveries	0		(2)				2		(4)
Charge-off of accounts	(2)	[1]	(4)	[1]			(4)	[1]	(4)	[1]
Financing Receivable, Allowance for Credit Losses, End of Period	$ 15		$ 28				$ 15		$ 28

[1] We repossess sold and leased vehicles on defaulted finance receivables and leases, and place them into Inventories. Losses recognized at the time of repossession and charged against the allowance for doubtful accounts were $1 million and $4 million for the three and nine months ended July 31, 2012, respectively, and $2 million and $17 million for the three and nine months ended July 31, 2011, respectively.