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Pension and Other Postretirement Plans (Tables) | 3 Months Ended
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Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract] |
Schedule of Net Periodic Benefit Costs | The following table presents the components of MGE Energy's and MGE's net periodic benefit costs recognized for the three months ended March 31, 2015 and 2014. A portion of the net periodic benefit cost is capitalized within the consolidated balance she ets.
|  |  | Three Months Ended |
|  |  | March 31, |
| (In thousands) |  | 2015 |  | 2014 |
| Pension Benefits |  |  |  |  |
| Components of net periodic cost (benefit): |  |  |  |  |
| Service cost | $ | 1,798 | $ | 1,484 |
| Interest cost |  | 3,440 |  | 3,251 |
| Expected return on assets |  | (5,677) |  | (5,279) |
| Amortization of: |  |  |  |  |
| Prior service cost |  | 6 |  | 49 |
| Actuarial loss |  | 1,334 |  | 173 |
| Net periodic cost (benefit) | $ | 901 | $ | (322) |
| Postretirement Benefits |  |  |  |  |
| Components of net periodic cost (benefit): |  |  |  |  |
| Service cost | $ | 383 | $ | 330 |
| Interest cost |  | 778 |  | 772 |
| Expected return on assets |  | (703) |  | (654) |
| Amortization of: |  |  |  |  |
| Transition obligation |  | 1 |  | 1 |
| Prior service benefit |  | (667) |  | (668) |
| Actuarial loss |  | 262 |  | 39 |
| Net periodic cost (benefit) | $ | 54 | $ | (180) |

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- Definition Tabular disclosure of the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920 + Details
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