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Fair Value of Financial Instruments Unobservable Input Reconciliation (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended
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Mar. 31, 2014 | Mar. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Balance as of the beginning of the period | $ 139 | $ 16
Net realized and unrealized (gains) losses (1) | (11) | 5
Purchases | 0 | 24
Transfers out of Level 3 to Level 2 | (3) | 0
Balance as of the end of the period | $ 131 | $ 45

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- Definition Net Liabilities From Price Risk Management Activities Classified as Level 3 + References No definition available. + Details
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- Definition Realized and Unrealized Gains and Losses, Net, Commodity Contracts + References No definition available. + Details
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- Details
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- Definition Amount of transfers of financial instrument classified as a liability out of level 3 of the fair value hierarchy. + 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 (c)(3) -URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258 + Details
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- Definition Amount of purchases of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + 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 (c)(2) -URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258 + Details
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