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Asset Retirement Obligations (Tables) | 12 Months Ended
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Dec. 31, 2011
Asset Retirement Obligation Disclosure [Abstract] |
Schedule of Asset Retirement Obligations [Table Text Block] | A reconciliation of ARO is as follows:
| PNMR |  | PNM |  | TNMP
| (In thousands)
Liability at December 31, 2008(1) | $ | 63,675 |  |  | $ | 62,879 |  |  | $ | 711 |
Liabilities incurred | 3,464 |  |  | 3,464 |  |  | — |
Liabilities settled | (8 | ) |  | (8 | ) |  | — |
Accretion expense | 5,751 |  |  | 5,683 |  |  | 60 |
Revisions to estimated cash flows (2) | (1,919 | ) |  | (1,919 | ) |  | — |
Liability at December 31, 2009 | 70,963 |  |  | 70,099 |  |  | 771 |
Liabilities incurred | 532 |  |  | 531 |  |  | — |
Liabilities settled | (603 | ) |  | (413 | ) |  | (190 | )
Accretion expense | 6,019 |  |  | 5,945 |  |  | 67 |
Revisions to estimated cash flows (2) | (274 | ) |  | (274 | ) |  | — |
Liability at December 31, 2010 | 76,637 |  |  | 75,888 |  |  | 648 |
Liabilities incurred | 60 |  |  | 60 |  |  | — |
Liabilities settled | (4 | ) |  | — |  |  | (4 | )
Accretion expense | 6,114 |  |  | 6,051 |  |  | 55 |
Revisions to estimated cash flows (2) | (3,574 | ) |  | (3,574 | ) |  | — |
Liability at December 31, 2011 | $ | 79,233 |  |  | $ | 78,425 |  |  | $ | 699 |
(1) | ARO for PNMR and PNM includes $0.2 million at December 31, 2008 for PNM Gas.
(2) | Based on studies to estimate amount and timing of future ARO expenditures. PNM has an ARO for PVNGS that includes the obligations for nuclear decommissioning of that facility. In 2011, a new decommissioning study for PVNGS reflects updated cash flow estimates and the 20-year license extension, which extends the commencement of decommissioning to 2045. The new study resulted in a $4.2 million decrease to the ARO.

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- Definition Tabular disclosure of the carrying amount of a liability for asset retirement obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Topic 410 -SubTopic 20 -Publisher FASB -Number -Article -Subparagraph -Name Accounting Standards Codification -Paragraph 1 -Section 50 -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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