2.2.0.7 true Fair Value Measurements - Additional Information (Detail) (USD $) 152 - Disclosure - Fair Value Measurements - Additional Information (Detail) true false In Millions false false 1 USD false false iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 2 USD false false iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 3 USD true false false false Other Operating Expense us-gaap_ComponentOfOtherOperatingCostAndExpenseGeneralAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_OtherOperatingExpenseMember us-gaap_ComponentOfOtherOperatingCostAndExpenseGeneralAxis explicitMember iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 4 USD true false false false Other Operating Expense us-gaap_ComponentOfOtherOperatingCostAndExpenseGeneralAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_OtherOperatingExpenseMember us-gaap_ComponentOfOtherOperatingCostAndExpenseGeneralAxis explicitMember iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 5 USD true false false false Fair Value, Inputs, Level 3 d_FairValueAssetsAndLiabilitiesComponentsAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_FairValueInputsLevel3Member d_FairValueAssetsAndLiabilitiesComponentsAxis explicitMember iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 6 USD true false false false Fair Value, Inputs, Level 3 d_FairValueAssetsAndLiabilitiesComponentsAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_FairValueInputsLevel3Member d_FairValueAssetsAndLiabilitiesComponentsAxis explicitMember false false Commodity us-gaap_TradingActivityByTypeAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_CommodityMember us-gaap_TradingActivityByTypeAxis explicitMember iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ 5 Commodity derivatives categorized as Level 3 fair value measurements, net asset 3 d_CommodityDerivatives d false debit instant This item represents the net balance of the entity's commodity derivatives categorized as Level 3 fair value measurements. false false false false false false false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 true true false false 17000000 17 true false false xbrli:monetaryItemType monetary This item represents the net balance of the entity's commodity derivatives categorized as Level 3 fair value measurements. No authoritative reference available. false 6 Commodity derivatives categorized as Level 3 fair value measurements, hypothetical 10% increase in commodity prices, decrease to net asset 3 d_SensitivityAnalysisOfCommodityDerivativesImpactOf10PercentIncreaseInCommodityPrices d false debit instant This item represents the amount of sensitivity associated with an increase in prices of the entity's commodity derivatives... false false false false false false false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false true false false -64000000 -64 true false false 6 false false false false 0 0 true false false xbrli:monetaryItemType monetary This item represents the amount of sensitivity associated with an increase in prices of the entity's commodity derivatives categorized as Level 3 fair value measurements. No authoritative reference available. false 7 Commodity derivatives categorized as Level 3 fair value measurements, hypothetical 10% decrease in commodity prices, increase to net asset 3 d_SensitivityAnalysisOfCommodityDerivativesImpactOf10PercentDecreaseInCommodityPrices d false credit instant This item represents the amount of sensitivity associated with a decrease in prices of the entity's commodity derivatives... false false false false false false false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false true false false 65000000 65 true false false 6 false false false false 0 0 true false false xbrli:monetaryItemType monetary This item represents the amount of sensitivity associated with a decrease in prices of the entity's commodity derivatives categorized as Level 3 fair value measurements. No authoritative reference available. false 8 State Line evaluation, impairment charge 3 us-gaap_ImpairmentOfLongLivedAssetsHeldForUse us-gaap true debit duration No definition available. false false false false false false false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false true false false 163000000 163 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 true false false xbrli:monetaryItemType monetary The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 144 -Paragraph 26 -Subparagraph b Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 144 -Paragraph 7, 25 false 9 State Line evaluation, impairment charge after tax 3 d_ImpairmentOfLongLivedAssetsHeldForUseNetOfTax d false debit duration Impairment of Long Lived Assets Held for Use, Net of Tax false false false false false false false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false true false false 95000000 95 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 true false false xbrli:monetaryItemType monetary Impairment of Long Lived Assets Held for Use, Net of Tax No authoritative reference available. false 10 State Line evaluation, estimated fair value 3 us-gaap_PropertyPlantAndEquipmentFairValueDisclosure us-gaap true debit instant No definition available. false false false false false false false false false false false false 1 false true false false 59000000 59 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 true false false xbrli:monetaryItemType monetary Tangible assets that are held by an entity for use in the production or supply of goods and services, for rental to others, or for administrative purposes and that are expected to provide economic benefit for more than one year; net of accumulated depreciation. Examples include land, buildings, and production equipment net of accumulated depreciation. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 157 -Paragraph 33 false 11 Equity method investment evaluation, impairment 3 us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment us-gaap true debit duration No definition available. false false false false false false false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false true false false 23000000 23 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 true false false xbrli:monetaryItemType monetary This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment. 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Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents investments accounted for under the equity method of accounting as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 6 -Subparagraph b false 6 8 false Millions UnKnown UnKnown false true