Legal Matters - Additional Information (Detail) (Class plaintiffs, USD $) In Millions, unless otherwise specified	6 Months Ended
	Mar. 31, 2013
Class plaintiffs
Loss Contingencies [Line Items]
Payments on litigation matters	$ 4,033	[1]

[1] These payments are associated with the Multidistrict Litigation Proceedings. The settlement with the class plaintiffs in these proceedings is subject to final court approval, which the Company cannot assure will be received, and to the adjudication of any appeals. See Note 11—Legal Matters.