Summary of Significant Accounting Policies Product Warranty Liability (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended				12 Months Ended
	Jul. 31, 2011	Apr. 30, 2011	Jul. 31, 2010	Apr. 30, 2009	Oct. 31, 2011		Oct. 31, 2010		Oct. 31, 2009
Accrued Product Warranty And Deferred Warranty Revenue, Standard And Extended Warranty Programs, Roll Forward:
Accrued product warranty and deferred warranty revenue, at beginning of period					$ 506		$ 492		$ 602
Cost accrued and revenues deferred					407		269		217
Acquisitions					5		0		0
Adjustments to pre-existing warranties	30	27	25	61	79	[1]	51	[1]	114	[1]
Payments and revenues recognized					(399)		(306)		(366)
Warranty adjustment related to legal settlement					0	[2]	0	[2]	(75)	[2]
Accrued product warranty and deferred warranty revenue, at end of period					598		506		492
Less: Current portion					(263)		(252)		(246)
Noncurrent accrued product warranty and deferred warranty revenue					335		254		246
Adjustments to pre-existing warranties, per diluted share	$ 0.39	$ 0.34	$ 0.34	$ 0.86
Extended Warranty Program:
Extended warranty program deferred revenue					257		167		139
Revenue recognized under extended warranty programs					$ 53		$ 46		$ 41
Minimum [Member]
Extended Warranty Program:
Product warranty period					1 year
Maximum [Member]
Extended Warranty Program:
Product warranty period					5 years

[1] Adjustments to pre-existing warranties reflect changes in our estimate of warranty costs for products sold in prior periods. Such adjustments typically occur when claims experience deviates from historic and expected trends. In the third quarter of 2011, we recorded adjustments for changes in estimates of $30 million, or $0.39 per diluted share. In the second quarter of 2011, we recorded adjustments for changes in estimates of $27 million, or $0.34 per diluted share. In the third quarter of 2010, we recorded adjustments for changes in estimates of $25 million, or $0.34 per diluted share. In the second quarter of 2009, we recorded material adjustments for changes in estimates of $61 million or $0.86 per diluted share.

[2] See Note 2, Restructurings and impairments, under Ford related restructuring activity for discussion regarding warranty adjustments related to the Ford Settlement.