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Commitments and Contingencies (Legal Proceedings) (Details) - 12 months ended Dec. 31, 2017 $ in Millions, $ in Millions | USD ($) | CAD ($) | USD ($)
--- | --- | --- | ---
Tampa Electric And Peoples Gas Division [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Loss Contingency, Estimate of Possible Loss |  | $ 38 | $ 30
Emera Maine [Member] | ISO New England OATT [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Loss Contingency, Estimate of Possible Loss |  |  | $ 4
TECO Guatemala Holdings [Member] | Prime Rate [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Litigation Settlement, Amount | $ 21 |  |

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