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Financial Instruments and Derivative Contracts - Assets and Liabilities Accounted for at Fair Value on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified | Dec. 31, 2011 | Dec. 31, 2010
--- | --- | ---
Assets |  |
Total assets | $ 4,870 | $ 3,298
Liabilities |  |
Total liabilities | 4,725 | 3,393
Net assets (liabilities) | 145 | (95)
Commodity Contract [Member] |  |
Assets |  |
Total assets | 4,826 | 3,263
Liabilities |  |
Total liabilities | 4,702 | 3,384
Interest rate derivatives [Member] |  |
Assets |  |
Total assets | 31 | 20
Foreign currency exchange derivatives [Member] |  |
Assets |  |
Total assets | 13 | 15
Liabilities |  |
Total liabilities | 23 | 9
Level 1 [Member] |  |
Assets |  |
Total assets | 2,807 | 1,456
Liabilities |  |
Total liabilities | 2,970 | 1,611
Net assets (liabilities) | (163) | (155)
Level 1 [Member] | Commodity Contract [Member] |  |
Assets |  |
Total assets | 2,807 | 1,456
Liabilities |  |
Total liabilities | 2,970 | 1,611
Level 2 [Member] |  |
Assets |  |
Total assets | 1,991 | 1,779
Liabilities |  |
Total liabilities | 1,745 | 1,746
Net assets (liabilities) | 246 | 33
Level 2 [Member] | Commodity Contract [Member] |  |
Assets |  |
Total assets | 1,947 | 1,744
Liabilities |  |
Total liabilities | 1,722 | 1,737
Level 2 [Member] | Interest rate derivatives [Member] |  |
Assets |  |
Total assets | 31 | 20
Level 2 [Member] | Foreign currency exchange derivatives [Member] |  |
Assets |  |
Total assets | 13 | 15
Liabilities |  |
Total liabilities | 23 | 9
Level 3 [Member] |  |
Assets |  |
Total assets | 72 | 63
Liabilities |  |
Total liabilities | 10 | 36
Net assets (liabilities) | 62 | 27
Level 3 [Member] | Commodity Contract [Member] |  |
Assets |  |
Total assets | 72 | 63
Liabilities |  |
Total liabilities | $ 10 | $ 36

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- Definition This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258 + Details
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- Definition Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 107 -Paragraph 10 -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 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 4, 17 -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. + Details
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- Definition This element represents the aggregate of the liabilities reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258 + Details
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