Financial Instruments (Schedule of Derivatives Fair Value Interest Rate) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Sep. 30, 2011
Eurobond (20% of $175 million) [Member]
Debt Instrument [Line Items]
Long-term debt	$ 175
Interest Rate Swap-Fixed to Variable [Member] \| Eurobond (20% of $175 million) [Member]
Debt Instrument [Line Items]
Percentage of debt hedged by interest rate derivatives	20.00%
Long-term debt	175
Notional amount of interest rate fair value hedge derivatives	35	35
Interest Rate Swap-Fixed to Variable [Member] \| Medium Term Notes [Member]
Debt Instrument [Line Items]
Notional amount of interest rate fair value hedge derivatives		$ 23

The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 21

-Paragraph 16, 20

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant