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Fair Value of Financial Instruments (Details-2) (USD $) | 3 Months Ended |
--- | --- | ---
Mar. 31, 2013 | Dec. 31, 2012
Deferred compensation interest calculation [Abstract] |  |
U.S Treasury Bills maturity | 26 |
Increase compounded monthly | 1.00% |
Minimum annual rate | 7.00% |
Assets: |  |
Exchange-traded investments | $ 428,000 | $ 320,000
Total Assets | 428,000 | 320,000
Liabilities: |  |
Derivatives, net | 69,197,000 | 72,329,000
Deferred compensation | 2,085,000 | 2,010,000
Total liabilities | 71,282,000 | 74,339,000
Derivative collateral | 500,000 | 0
Level 1 [Member] |  |
Assets: |  |
Exchange-traded investments | 428,000 | 320,000
Total Assets | 428,000 | 320,000
Liabilities: |  |
Derivatives, net | (401,000) | (17,000)
Deferred compensation | 0 | 0
Total liabilities | (401,000) | (17,000)
Level 2 [Member] |  |
Assets: |  |
Exchange-traded investments | 0 | 0
Total Assets | 0 | 0
Liabilities: |  |
Derivatives, net | 0 | 0
Deferred compensation | 2,085,000 | 2,010,000
Total liabilities | 2,085,000 | 2,010,000
Level 3 [Member] |  |
Assets: |  |
Exchange-traded investments | 0 | 0
Total Assets | 0 | 0
Liabilities: |  |
Derivatives, net | 69,598,000 | 72,346,000
Deferred compensation | 0 | 0
Total liabilities | 69,598,000 | 72,346,000
MGE [Member] |  |
Assets: |  |
Exchange-traded investments | 161,000 | 117,000
Total Assets | 161,000 | 117,000
Liabilities: |  |
Derivatives, net | 69,197,000 | 72,329,000
Deferred compensation | 2,085,000 | 2,010,000
Total liabilities | 71,282,000 | 74,339,000
Derivative collateral | 500,000 | 0
MGE [Member] | Level 1 [Member] |  |
Assets: |  |
Exchange-traded investments | 161,000 | 117,000
Total Assets | 161,000 | 117,000
Liabilities: |  |
Derivatives, net | (401,000) | (17,000)
Deferred compensation | 0 | 0
Total liabilities | (401,000) | (17,000)
MGE [Member] | Level 2 [Member] |  |
Assets: |  |
Exchange-traded investments | 0 | 0
Total Assets | 0 | 0
Liabilities: |  |
Derivatives, net | 0 | 0
Deferred compensation | 2,085,000 | 2,010,000
Total liabilities | 2,085,000 | 2,010,000
MGE [Member] | Level 3 [Member] |  |
Assets: |  |
Exchange-traded investments | 0 | 0
Total Assets | 0 | 0
Liabilities: |  |
Derivatives, net | 69,598,000 | 72,346,000
Deferred compensation | 0 | 0
Total liabilities | $ 69,598,000 | $ 72,346,000

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