Commitments and contingencies (Details) In Millions, unless otherwise specified	1 Months Ended	0 Months Ended	3 Months Ended	0 Months Ended		12 Months Ended				3 Months Ended			3 Months Ended
	Jan. 31, 2012 USD ($) site	Jan. 31, 2012 Pending or Threatened Litigation [Member] FATMA Notice, Trial [Member] Penalties [Member] USD ($)	Jan. 31, 2012 Pending or Threatened Litigation [Member] FATMA Notice, Trial [Member] Penalties [Member] BRL	Jan. 31, 2012 Pending or Threatened Litigation [Member] Lis Franco vs. Syntex and MWM, Trial [Member] USD ($)	Oct. 25, 2011 Pending or Threatened Litigation [Member] Lis Franco vs. Syntex and MWM, Trial [Member] BRL	Dec. 31, 1999 Pending or Threatened Litigation [Member] Lis Franco vs. Syntex and MWM, Trial [Member] Royalties [Member] BRL	Jan. 31, 2012 Pending or Threatened Litigation [Member] Lis Franco vs. Syntex and MWM, Trial [Member] Royalties [Member] USD ($)	May 30, 2010 Pending or Threatened Litigation [Member] Lis Franco vs. Syntex and MWM, Trial [Member] Royalties [Member] BRL	Dec. 31, 2009 Pending or Threatened Litigation [Member] Lis Franco vs. Syntex and MWM, Trial [Member] Royalties [Member] BRL	Jan. 31, 2012 Damages from Product Defects [Member] Kruse Technology vs. Ford Motor Company [Member] patents	Jan. 31, 2012 G E Operating Agreement [Member] USD ($)	Oct. 31, 2011 G E Operating Agreement [Member] USD ($)	Jan. 31, 2012 Minimum [Member]	Jan. 31, 2012 Maximum [Member]
Loss Contingencies [Line Items]
Length of Agreement											3 years
Length Of Potential Automatic Extension Years											1 year
Operating Agreement Excess Loss Percentage											10.00%
Outstanding finance receivables, off-balance sheet											$ 875	$ 723
Related originations of outstanding finance receivables, off-balance sheet											1,000	818
Historical losses on finance receivables, measured as percentage of average balance of related finance receivable													0.30%	2.10%
Available stand-by letters of credit and surety bonds	121
Unused credit commitments outstanding	33
Purchase commitments	130
Long Term Purchase Commitment Cancellation Fees	31
Number of Contaminated Sites	2
Accrual for environmental loss contingencies	20
Damages sought, value		1.20	2.00	6.40	10.85	42.00
Potential patent infringement, number of patents										3
Estimate of possible loss						16.0	$ 43.0	74.0	70.0