Restructuring Costs (Details Textuals) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended				6 Months Ended	12 Months Ended		3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended
	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011	Sep. 30, 2011	Sep. 30, 2010	Mar. 31, 2012 Commercial Truck Segment [Member]	Sep. 30, 2007 Performance Plus Program [Member]	Mar. 31, 2012 Employee Severance [Member]	Dec. 31, 2011 St Priest [Member]	Mar. 31, 2012 St Priest [Member]	Dec. 31, 2011 European Action [Member]	Mar. 31, 2012 European Action [Member]
Restructuring Reserve	$ 15		$ 17	$ 15	$ 17	$ 19	$ 11
Restructuring and Related Cost, Expected Number Of Positions Eliminated									2,800
Restructuring Reserve, Period Expense								24
Cumulative Restructuring Costs Performance Plus Program Discontinued Operations	93			93
Cumulative Employee Severance and Related Cost Under Peformance Plus Program										117
Cumulative Restructuring Costs Performance Plus Program	186			186
Cumulative Restructuring Costs Under Performance Plus Program Related To Commercial Truck Segment	82			82
Cumulative Restructuring Costs Under Performance Plus Program Related To Corporate Locations and Aftermarket and Trailer Segment	11			11
Cumulative Restructuring Cost Asset Impairment Charges Under Performance Plus Program	41			41
Cumulative Restructuring Cost Pension Termination Benefits Under Performance Plus Program	28			28
Total Expected European Action Restructuring Costs														5
Restructuring Costs and Asset Impairment Charges		19		20	1						17
Restructuring Charges	$ 3		$ 5	$ 27	$ 8						$ 1	$ 5	$ 1