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Asset Retirement Obligations (Tables) | 12 Months Ended
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Dec. 31, 2011
Asset Retirement Obligations [Abstract] |
Schedule Of Changes In Asset Retirement Obligations |
|  |  | September 30, |  |  |  | September 30, |
|  | December 31, |
|  | 2011 |  |  | 2010 |
|  | (In thousands) |
Asset retirement obligation — beginning of period |  | $ | 7,640 |  |  | $ | 6,511 |
Liabilities incurred during period |  |  | 4,100 |  |  |  | 1,747 |
Liabilities settled during period |  |  | (369 | ) |  |  | (422 | )
Accretion expense during period |  |  | 590 |  |  |  | 414 |
Revisions to estimates |  |  | 1,114 |  |  |  | (610 | )
Asset retirement obligation — end of period |  | $ | 13,075 |  |  | $ | 7,640 |

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- Definition Tabular disclosure of the changes in carrying amount of a liability for asset retirement obligations, for changes such as new obligations, changes in estimates of existing obligations, spending on existing obligations, property dispositions, and foreign currency translation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Topic 410 -SubTopic 30 -Publisher FASB -Number -Article -Subparagraph -Name Accounting Standards Codification -Paragraph 5 -Section 50 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13201-110859 + Details
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