Financial Statements - Carrying Amounts and Classification of Assets and Liabilities for Consolidated VIEs (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Variable Interest Entity [Line Items]
Current assets	$ 12,381us-gaap_AssetsCurrent	$ 13,107us-gaap_AssetsCurrent	$ 12,726us-gaap_AssetsCurrent
Current liabilities	11,387us-gaap_LiabilitiesCurrent	11,694us-gaap_LiabilitiesCurrent	11,803us-gaap_LiabilitiesCurrent
Noncurrent liabilities	9,025us-gaap_LiabilitiesNoncurrent	9,354us-gaap_LiabilitiesNoncurrent	7,068us-gaap_LiabilitiesNoncurrent
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Current assets	184	218	212
Noncurrent assets	136	138	140
Total assets	320	356	352
Current liabilities	155	189	171
Noncurrent liabilities	36	37	39
Total liabilities	$ 191	$ 226	$ 210

Sum of the carrying amounts as of the balance sheet date of all assets that are expected to be realized in cash, sold, or consumed within one year (or the normal operating cycle, if longer). Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.9)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6801-107765

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 9

-Article 5

+ Details

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

- Definition

Sum of the carrying amounts as of the balance sheet date of all assets that are expected to be realized in cash, sold or consumed after one year or beyond the normal operating cycle, if longer.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 18

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.10-17)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Total obligations incurred as part of normal operations that are expected to be paid during the following twelve months or within one business cycle, if longer.

+ References

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of obligation due after one year or beyond the normal operating cycle, if longer.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (bb)

-URI http://asc.fasb.org/extlink&oid=28200181&loc=d3e5710-111685

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- Definition

The carrying amount of the consolidated Variable Interest Entity's liabilities included in the reporting entity's statement of financial position.

+ References

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