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Regulatory Assets and Liabilities - Florida Electric Utility (Narrative) (Details) $ in Millions, $ in Millions |  |  |  |  |  | 1 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Feb. 01, 2021 USD ($) | Aug. 03, 2020 USD ($) | Jun. 09, 2020 USD ($) | Apr. 27, 2020 USD ($) | Aug. 20, 2018 USD ($) | Jan. 31, 2020 USD ($) | Dec. 31, 2020 CAD ($) MW | Dec. 31, 2020 USD ($) MW | Dec. 31, 2019 CAD ($) | Dec. 31, 2020 USD ($) | Jun. 01, 2020 CAD ($) | Jun. 01, 2020 USD ($)
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
State income tax |  |  |  |  |  |  | 26.00% | 26.00% | 8.00% |  |  |
Utilities Operating Expense, Depreciation and Amortization |  |  |  |  |  |  | $ 881 |  | $ 903 |  |  |
Florida Electric Utility | Operating |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Utilities Operating Expense, Depreciation and Amortization |  |  |  |  |  |  | $ 455 |  | $ 445 |  |  |
Tampa Electric | SoBRA | Florida Electric Utility | Operating |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Property, Plant and Equipment, Generation or Processing |  |  |  |  |  |  |  |  |  | $ 820 |  |
Estimated revenue in MW | MW |  |  |  |  |  |  | 600 | 600 |  |  |  |
Tampa Electric | SoBRA | Scenario Plan | Florida Electric Utility | Operating |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Property, Plant and Equipment, Generation or Processing |  |  |  |  |  |  |  |  |  | 30 |  |
Tampa Electric | Florida Public Service Commission | Florida Electric Utility | Operating |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Disclosure of Rate Matters |  |  |  |  |  |  | Tampa Electric is regulated by the FPSC. Tampa Electric is also subject to regulation by the Federal Energy Regulatory Commission (“FERC”). The FPSC sets rates at a level that allows utilities such as Tampa Electric to collect total revenues or revenue requirements equal to their cost of providing service, plus an appropriate return on invested capital. | Tampa Electric is regulated by the FPSC. Tampa Electric is also subject to regulation by the Federal Energy Regulatory Commission (“FERC”). The FPSC sets rates at a level that allows utilities such as Tampa Electric to collect total revenues or revenue requirements equal to their cost of providing service, plus an appropriate return on invested capital. |  |  |  |
Allowed equity capital structure |  |  |  |  |  |  | 54.00% | 54.00% |  |  |  |
Public Utilities, Approved Rate Increase (Decrease), Amount |  | $ 15 |  |  | $ 103 |  |  | $ 5 |  |  |  |
Storm Damage Provision |  | $ 39 |  | $ 15 |  | $ 12 |  |  |  |  |  |
Accumulated Depreciation, Depletion and Amortization, Property, Plant and Equipment, Period Increase (Decrease) |  |  | $ 16 |  |  |  |  |  |  |  |  |
Tampa Electric | Florida Public Service Commission | Cost recovery clauses | Florida Electric Utility | Operating |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Approved regulated return on equity |  |  |  |  |  |  | 10.25% | 10.25% |  |  |  |
Tampa Electric | Florida Public Service Commission | SoBRA | Florida Electric Utility | Operating |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Estimated revenue in MW | MW |  |  |  |  |  |  | 600 | 600 |  |  |  |
Estimated revenue |  |  |  |  |  |  |  | $ 104 |  |  |  |
Tampa Electric | Florida Public Service Commission | Big Bend Modernization Project | Unit 1 components | Florida Electric Utility | Operating |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Property, Plant and Equipment, Generation or Processing |  |  |  |  |  |  |  |  |  | 526 |  |
Public Utilities, Property, Plant and Equipment, Plant in Service |  |  |  |  |  |  | $ 255 |  |  | 200 | $ 304 | $ 223
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation |  |  |  |  |  |  | $ 112 |  |  | $ 88 | $ 123 | $ 90
Tampa Electric | Florida Public Service Commission | Big Bend Modernization Project | Subsequent Event | Florida Electric Utility | Operating |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Requested Rate Increase (Decrease), Amount | $ 130 |  |  |  |  |  |  |  |  |  |  |
Tampa Electric | Florida Public Service Commission | Range, Minimum | Florida Electric Utility | Operating |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Approved regulated return on equity |  |  |  |  |  |  | 9.25% | 9.25% | 9.25% |  |  |
Tampa Electric | Florida Public Service Commission | Range, Minimum | Subsequent Event | Florida Electric Utility | Operating |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Storm Damage Provision | 280 |  |  |  |  |  |  |  |  |  |  |
Tampa Electric | Florida Public Service Commission | Range, Maximum | Florida Electric Utility | Operating |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Approved regulated return on equity |  |  |  |  |  |  | 11.25% | 11.25% | 11.25% |  |  |
Tampa Electric | Florida Public Service Commission | Range, Maximum | Subsequent Event | Florida Electric Utility | Operating |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Storm Damage Provision | $ 295 |  |  |  |  |  |  |  |  |  |  |

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