Pension and Other Benefit Programs - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
Mar. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Pension and postretirement medical plans, employer contributions	$ 99
Minimum
Defined Benefit Plan Disclosure [Line Items]
Expected pension and postretirement medical plan contributions	325
Maximum
Defined Benefit Plan Disclosure [Line Items]
Expected pension and postretirement medical plan contributions	$ 375

The increase in the fair value of plan assets from contributions made by the employer.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)(3)

-URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e1928-114920

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration