Restructuring (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				15 Months Ended	3 Months Ended								15 Months Ended	9 Months Ended		3 Months Ended	15 Months Ended	9 Months Ended		3 Months Ended	15 Months Ended	3 Months Ended			9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended
	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2012 Fort Wayne, Springfield, Chatham and Custom Products [Member]	Jan. 31, 2011 Fort Wayne And Springfield [Member] Truck [Member]	Jan. 31, 2012 Fort Wayne And Springfield [Member] Truck [Member]	Jan. 31, 2012 Chatham [Member] Truck [Member] Minimum [Member]	Jan. 31, 2012 Chatham [Member] Truck [Member] Maximum [Member]	Jan. 31, 2012 Custom Products [Member] Truck [Member]	Jan. 31, 2012 Custom Products [Member] Truck [Member] Minimum [Member]	Jan. 31, 2012 Custom Products [Member] Truck [Member] Maximum [Member]	Jan. 31, 2012 Facility Relocation, Expansion and Development [Member] Minimum [Member]	Jan. 31, 2012 Facility Relocation, Expansion and Development [Member] Maximum [Member]	Jan. 31, 2012 Employee Termination Charges [Member] Fort Wayne, Springfield, Chatham and Custom Products [Member]	Jan. 31, 2012 Employee Termination Charges [Member] Fort Wayne And Springfield [Member] Truck [Member]	Jan. 31, 2012 Employee Termination Charges [Member] Chatham [Member] Truck [Member]	Jan. 31, 2012 Employee Termination Charges [Member] Custom Products [Member] Truck [Member]	Jan. 31, 2011 Employee Termination Charges [Member] Location Springfield Assembly Plant [Member] Truck [Member]	Jan. 31, 2012 Pension and Other Postretirement Contractual Termination Benefits [Member] Fort Wayne And Springfield [Member] Truck [Member]	Jan. 31, 2012 Pension and Other Postretirement Contractual Termination Benefits [Member] Chatham [Member] Truck [Member]	Jan. 31, 2012 Pension and Other Postretirement Contractual Termination Benefits [Member] Custom Products [Member] Truck [Member]	Jan. 31, 2012 Employee Relocation Costs [Member] Fort Wayne, Springfield, Chatham and Custom Products [Member]	Jan. 31, 2012 Employee Relocation Costs [Member] Fort Wayne And Springfield [Member] Truck [Member]	Jul. 31, 2011 Facility Closing [Member] Chatham [Member] Truck [Member]	Oct. 31, 2011 Facility Closing [Member] Custom Products [Member] Truck [Member]	Jul. 31, 2011 Facility Closing [Member] Custom Products [Member] Truck [Member]	Jan. 31, 2012 Facility Closing [Member] Custom Products [Member] Truck [Member]	Jan. 31, 2012 Other Contractual Costs [Member] Fort Wayne, Springfield, Chatham and Custom Products [Member]	Jan. 31, 2012 Other Contractual Costs [Member] Chatham [Member] Truck [Member]	Jan. 31, 2011 Ford [Member] Employee Termination Charges [Member] Location IEP And ICC [Member]	Jan. 31, 2012 Tax Exempt Bond [Member] Manufacturing Operations [Member]
Restructuring Cost and Reserve [Line Items]
Debt Instrument, Interest Rate, Stated Percentage																														6.50%
Restructuring charges (benefit)	$ 0	$ 22		$ 18	$ 29									$ 13	$ 7	$ 6	$ 4	$ 7	$ 33	$ 4		$ 9	$ 48	$ 5	$ 5	$ 10		$ 8
Expected restructuring and related charges						30	70		5	10	70	90
Restructuring Charges Length Of Payment Period								2 years
Restructuring Reserve [Roll Forward]
Restructuring liability, balance at beginning of period			39										31								0						8		5
Additions			2										1								1						0		17
Payments			(10)										(2)								(1)						(7)		(3)
Adjustments			(2)										(2)								0						0		0
Restructuring liability, balance at end of period			$ 29										$ 28								$ 0						$ 1		$ 19