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Subsequent Events - Additional Information (Detail) (Subsequent Event [Member]) | Jan. 31, 2013 Barrels
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2013 swaps and three-way costless collar options [Member] |
Subsequent Event [Line Items] |
Total notional amount of oil barrels | 334,000
2014 swaps and three-way costless collar options [Member] |
Subsequent Event [Line Items] |
Total notional amount of oil barrels | 699,000
2015 swaps and three-way costless collar options [Member] |
Subsequent Event [Line Items] |
Total notional amount of oil barrels | 62,000

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- Definition Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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Namespace Prefix: | invest_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

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- Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration