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Asset Retirement Obligations (Tables) | 12 Months Ended
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Dec. 31, 2015
Asset Retirement Obligation Disclosure [Abstract] |
Change in Asset Retirement Obligations | The following table shows a rollforward of the AROs from January 1, 2014, to December 31, 2015. Amounts include conditional AROs.
| (In thousands) |  | 2015 |  | 2014 |
| Balance at January 1, | $ | 19,744 | $ | 19,359 |
| Liabilities incurred (a) |  | 2,380 |  | 68 |
| Accretion expense |  | 1,131 |  | 1,077 |
| Liabilities settled |  | (124) |  | (343) |
| Revisions in estimated cash flows (a) |  | 1,229 |  | (417) |
| Balance at December 31, | $ | 24,360 | $ | 19,744 |
(a) In the second quarter of 2015, MGE recorded an obligation of $2.3 million for the fair value of its legal liability for AROs associated with the effect of the final Coal Combustion Residual Rule at Columbia. An additional $1.3 million was recorded in the fourth quarter, associated with this ARO, based on revised estimates.

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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 -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13201-110859 + Details
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