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Intangible Assets | 12 Months Ended
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Dec. 31, 2024
Goodwill and Intangible Assets Disclosure [Abstract] |
Intangible Assets | Intangible Assets We have a coal supply agreement intangible asset which is subject to amortization based on units of production over the term of the lignite sales agreement which expires in 2032. The gross and net balances are set forth in the following table:
| Gross Carrying Amount |  | Accumulated Amortization and Impairment |  | Net Balance
Balance at December 31, 2024 |  |  |  |  |
Coal supply agreement | $ | 84,200 |  |  | $ | (78,725) |  |  | $ | 5,475 |
Balance at December 31, 2023 |  |  |  |  |
Coal supply agreement | $ | 84,200 |  |  | $ | (78,194) |  |  | $ | 6,006 |
Amortization expense for intangible assets was $0.5 million and $3.0 million in 2024 and 2023, respectively. During 2023, we recorded a non-cash, long-lived asset impairment charge of $65.9 million. See Note 9 for further discussion of the impairment charge.

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- Definition The entire disclosure for goodwill and intangible assets. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Publisher FASB -URI https://asc.fasb.org/350-30/tableOfContent Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Publisher FASB -URI https://asc.fasb.org/350-20/tableOfContent + Details
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