Acquisitions and Divestitures - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended				12 Months Ended	6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012 Divestitures	Mar. 31, 2013 Divestitures Acquisition	Sep. 30, 2012	Mar. 31, 2012 Acquisition	Mar. 31, 2012 Purchase Price True-Up	Sep. 30, 2012 Purchase Price True-Up	Mar. 31, 2013 Purchase Price	Mar. 31, 2012 Purchase Price	Mar. 31, 2012 Power Solutions	Mar. 31, 2012 Automotive Experience
Acquisitions And Discontinued Operations [Line Items]
Number of acquisitions			2		3
Acquisition of businesses, net of cash acquired	$ 113	$ 19	$ 113		$ 30	$ 8		$ 113	$ 38
Goodwill related to acquisition	177	71	177		71
Number of divestitures		2	0
Number of acquisitions which increased Company's ownership from noncontrolling to controlling interest			1		2
Aggregate non-cash gain recorded due to acquisition	82	12	82		12					9	3
Goodwill adjustment							13
Sales price of divestiture	0	91	0		91
Net gain on divestitures		35
Reduction in goodwill related to business divestitures		$ 29	$ 0	$ 5