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Summary of Significant Accounting Policies Fuel Inventories (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2014
--- | --- | --- | ---
Other | $ 29.5 | $ 54.6 |
Public Utilities, Inventory, Fuel [Member] |  |  |
Public Utilities, Inventory | $ 57.6 | $ 84.3 |
Other Assets |  |  | $ 11.0

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