Commitments and contingencies (Details)	1 Months Ended		0 Months Ended	3 Months Ended	0 Months Ended		12 Months Ended					3 Months Ended		6 Months Ended	3 Months Ended		3 Months Ended
	Jan. 31, 2012 USD ($)	Apr. 30, 2012 USD ($) site	Jan. 31, 2012 Pending or Threatened Litigation [Member] FATMA Notice, Trial [Member] Penalties [Member] USD ($)	Apr. 30, 2012 Pending or Threatened Litigation [Member] FATMA Notice, Trial [Member] Penalties [Member] BRL	Jan. 31, 2012 Pending or Threatened Litigation [Member] Lis Franco vs. Syntex and MWM, Trial [Member] USD ($)	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	Apr. 30, 2012 Pending or Threatened Litigation [Member] Lis Franco vs. Syntex and MWM, Trial [Member] Royalties [Member] USD ($)	May 30, 2010 Pending or Threatened Litigation [Member] Lis Franco vs. Syntex and MWM, Trial [Member] Royalties [Member] BRL	Dec. 31, 2009 Pending or Threatened Litigation [Member] Lis Franco vs. Syntex and MWM, Trial [Member] Royalties [Member] BRL	Apr. 30, 2012 Damages from Product Defects [Member] USD ($)	Apr. 30, 2012 Damages from Product Defects [Member] Kruse Technology vs. Ford Motor Company [Member] patents	Apr. 30, 2012 Damages from Product Defects [Member] Non-conformance Penalties [Member] Penalties [Member] USD ($)	Apr. 30, 2012 Damages from Product Defects [Member] Non-conformance Penalties [Member] Penalties [Member] USD ($)	Apr. 30, 2012 G E Operating Agreement [Member] USD ($)	Oct. 31, 2011 G E Operating Agreement [Member] USD ($)	Apr. 30, 2012 Minimum [Member]	Apr. 30, 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															$ 1,043,000,000	$ 723,000,000
Related originations of outstanding finance receivables, off-balance sheet															1,240,000,000,000	818,000,000
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		98,000,000
Unused credit commitments outstanding		33,000,000
Purchase commitments	127,000,000
Long Term Purchase Commitment Cancellation Fees	30,000,000
Number of Contaminated Sites		2
Accrual for environmental loss contingencies		20,000,000
Damages sought, value			1,050,000	2,000,000	5,700,000	10,850,000	42,000,000						10,000,000	1,919,000,000
Notive of Violation, number											7,600
Potential patent infringement, number of patents												3
Estimate of possible loss							16,000,000	$ 38,800,000	74,000,000	70,000,000