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Subsequent Events (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Mar. 31, 2012 | Apr. 03, 2012 Amended Credit Facility [Member] | Oct. 06, 2011 Amended Credit Facility [Member] | Feb. 02, 2011 Amended Credit Facility [Member] | May 01, 2012 2012 Two-Way And Three-Way Collars [Member] | May 01, 2012 2013 Two-Way And Three-Way Collars [Member] | May 01, 2012 2014 Two-Way And Three-Way Collars [Member] | May 01, 2012 2015 Two-Way And Three-Way Collars [Member]
Subsequent Event [Line Items] |  |  |  |  |  |  |  |
Term of contract | 1 |  |  |  |  |  |  |
Line of credit facility amount outstanding |  | $ 500.0 | $ 350.0 | $ 137.5 |  |  |  |
Total notional amount, in barrels |  |  |  |  | 306,000 | 730,000 | 730,000 | 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 + Details
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