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Regulatory Assets and Liabilities (Storm reserve & Solar investment) (Details) $ in Millions, $ in Millions | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2017 USD ($) MW | Dec. 31, 2016 USD ($) | Dec. 31, 2017 CAD ($) | Dec. 31, 2017 USD ($) | Sep. 10, 2017 USD ($) | Dec. 31, 2016 CAD ($)
Regulatory Assets [Line Items] |  |  |  |  |  |
Regulatory Assets |  |  | $ 1,376 |  |  | $ 1,322
Tampa Electric Division [Member] | Tropical Storm Colin, Hurricane Hermine and Hurricane Matthew Restoration [Member] | OM&G [Member] | Other Regulatory Assets (Liabilities) [Member] | LossFromCatastrophesMember |  |  |  |  |  |
Regulatory Assets [Line Items] |  |  |  |  |  |
Storm cost |  | $ 10 |  |  |  |
Tampa Electric Division [Member] | Hurricane Irma Restoration [Member] | OM&G [Member] | Capital Expenditures [Member] | LossFromCatastrophesMember |  |  |  |  |  |
Regulatory Assets [Line Items] |  |  |  |  |  |
Storm Reserve |  |  |  |  | $ 8 |
Tampa Electric Division [Member] | Hurricane Irma Restoration [Member] | OM&G [Member] | Other Regulatory Assets (Liabilities) [Member] | LossFromCatastrophesMember |  |  |  |  |  |
Regulatory Assets [Line Items] |  |  |  |  |  |
Storm cost | $ 4 |  |  |  |  |
Storm Reserve |  |  |  |  | $ 93 |
Tampa Electric Division [Member] | SoBRA [Member] | Capital Expenditures [Member] |  |  |  |  |  |
Regulatory Assets [Line Items] |  |  |  |  |  |
Estimated Investement in projects |  |  |  | $ 850 |  |
Capacity Of Utility Project | MW | 600 |  |  |  |  |
Estimated revenue | $ 26 |  |  |  |  |
Estimated revenue in MW | MW | 145 |  |  |  |  |

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- Definition Carrying amount as of the balance sheet date of capitalized storm costs of a regulated entity that are expected to be recoverable through rate adjustments after one year or beyond the normal operating cycle, if longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=77907324&loc=d3e43603-110378 + Details
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- Definition The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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- Definition A noncash adjustment to the provision established for storm damage by an oil, gas, or utility company. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585 + Details
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