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Summary of Significant Accounting Policies Fuel Inventories (Details) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2014
--- | --- | --- | ---
Other | $ 54.6 | $ 81.8 |
Public Utilities, Inventory, Fuel [Member] |  |  |
Public Utilities, Inventory | 84.3 | $ 82.4 |
Other Assets |  |  | $ 11.0
Other | $ 2.8 |  |

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- Definition Amount of current assets classified as other. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.8) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The period end amount for a type of inventory held by the utility in a schedule of inventories. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-05.6(a)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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