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Regulatory Matters - Boswell Mercury Emission Reduction Plan (Details) (Boswell Unit 4 [Member], USD $) In Millions, unless otherwise specified | Dec. 31, 2012
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Boswell Unit 4 [Member] |
Schedule of Utility Generating Facilities [Line Items] |
Estimated Environmental Compliance Costs - Minimum | $ 350
Estimated Environmental Compliance Costs - Maximum | $ 400

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