Derivatives (Schedule of Derivatives Fair Value Interest Rate) (Detail) (Eurobond 20% [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Sep. 30, 2012
Derivative [Line Items]
Long-term debt	$ 175
Interest Rate Swap-Fixed to Variable [Member]
Derivative [Line Items]
Percentage of debt hedged by interest rate derivatives	20.00%
Long-term debt	175
Fair Value Hedging [Member] | Interest Rate Swap-Fixed to Variable [Member]
Derivative [Line Items]
Notional amount of interest rate fair value hedge derivatives	$ 35	$ 35