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Regulatory Assets and Liabilities - Gas Utilities and Infrastructure (Narrative) (Details) $ in Millions, $ in Millions |  | 1 Months Ended | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | ---
Jul. 17, 2019 USD ($) | Jan. 31, 2021 USD ($) | Sep. 30, 2019 CAD ($) | Sep. 30, 2019 USD ($) | Dec. 31, 2020 CAD ($) | Dec. 31, 2019 CAD ($) | Dec. 31, 2020 USD ($) km | Dec. 31, 2018 CAD ($) | Dec. 31, 2018 USD ($)
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Income tax expense (recovery) |  |  |  |  | $ (341) | $ (61) |  |  |
Gas Utilities and Infrastructure | Operating |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Income tax expense (recovery) |  |  |  |  | $ (51) | $ (48) |  |  |
Emera Brunswick Pipeline Company Limited | Gas Utilities and Infrastructure |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Length Of Pipeline | km |  |  |  |  |  |  | 145 |  |
Emera Brunswick Pipeline Company Limited | Gas Utilities and Infrastructure | Operating |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Length Of Pipeline | km |  |  |  |  |  |  | 145 |  |
Public Utilities, Property, Plant and Equipment, Transmission and Distribution, Useful Life |  |  |  |  | 25 years |  |  |  |
NMGC | Gas Utilities and Infrastructure | Operating |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Approved regulated return on equity |  |  |  |  | 9.10% |  |  |  |
Public Utilities, Phase-in Plan Terms |  |  |  |  | On July 17, 2019, the NMPRC approved a rate increase for NMGC effective August 2019 and allowed NMGC to retain tax reform benefits realized from January 1, 2018 to the effective date of the new rates. The new rates were phased in over two years, resulting in an annual revenue increase of approximately $3 million USD. |  |  |  |
Deferred Tax Liabilities, Regulatory Assets and Liabilities |  |  |  |  |  |  |  | $ 11 | $ 8
Income tax expense (recovery) |  |  | $ 7 | $ 5 |  |  |  |  |
NMGC | Range, Minimum | Gas Utilities and Infrastructure | Operating |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Approved regulated return on equity |  |  |  |  |  | 9.10% |  |  |
NMGC | Range, Maximum | Gas Utilities and Infrastructure | Operating |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Approved regulated return on equity |  |  |  |  |  | 10.00% |  |  |
NMGC | New Mexico Public Regulatory | Gas Utilities and Infrastructure | Operating |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Phase-in Plan, Amount of Capitalized Costs Recovered | $ 3 |  |  |  |  |  |  |  |
NMGC | New Mexico Public Regulatory | Gas Utilities and Infrastructure | Operating | Scenario Plan |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Approved regulated return on equity |  | 9.375% |  |  |  |  |  |  |
Allowed equity capital structure |  | 52.00% |  |  |  |  |  |  |
Phase-in Plan, Amount of Capitalized Costs Recovered |  | $ 5 |  |  |  |  |  |  |
PGS | Gas Utilities and Infrastructure | Operating |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Approved regulated return on equity |  |  |  |  | 10.75% |  |  |  |
Allowed equity capital structure |  |  |  |  | 54.70% |  |  |  |
Length Of Pipeline, percentage |  |  |  |  |  |  | 5.00% |  |
Length Of Pipeline | km |  |  |  |  |  |  | 800 |  |
Replacement program |  |  |  |  |  |  | $ 80 |  |
Regulatory Asset Amortization Period |  |  |  |  | 10 years |  |  |  |
Public Utilities, Disclosure of Rate Matters |  |  |  |  | PGS was permitted to initiate a general base rate proceeding during 2020, provided the new rates do not become effective before January 1, 2021. On June 8, 2020, PGS filed a petition for an increase in rates and service charges effective January 2021. On November 19, 2020, the FPSC approved a settlement agreement filed by PGS. |  |  |  |
PGS | Gas Utilities and Infrastructure | Operating | Scenario Plan |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Accumulated Depreciation, Depletion and Amortization, Property, Plant and Equipment, Period Increase (Decrease) |  | 34 |  |  |  |  |  |  |
Phase-in Plan, Amount of Capitalized Costs Recovered |  | 34 |  |  |  |  |  |  |
Public Utilities, Approved Rate Increase (Decrease), Amount |  | 58 |  |  |  |  |  |  |
PGS | Gas Utilities and Infrastructure | Operating | Cast Iron/Bare Steel Pipe Replacement |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Length Of Pipeline | km |  |  |  |  |  |  | 880 |  |
PGS | Gas Utilities and Infrastructure | Operating | Cast Iron/Bare Steel Pipe Replacement | Scenario Plan |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Phase-in Plan, Amount of Capitalized Costs Recovered |  | $ 24 |  |  |  |  |  |  |
PGS | Range, Minimum | Gas Utilities and Infrastructure | Operating |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Approved regulated return on equity |  |  |  |  | 9.25% | 9.25% |  |  |
PGS | Range, Minimum | Gas Utilities and Infrastructure | Operating | Scenario Plan |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Approved regulated return on equity |  | 8.90% |  |  |  |  |  |  |
Allowed equity capital structure |  | 54.70% |  |  |  |  |  |  |
PGS | Range, Maximum | Gas Utilities and Infrastructure | Operating |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Approved regulated return on equity |  |  |  |  | 11.75% | 11.75% |  |  |
PGS | Range, Maximum | Gas Utilities and Infrastructure | Operating | Scenario Plan |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Approved regulated return on equity |  | 11.00% |  |  |  |  |  |  |
PGS | Mid Point | Gas Utilities and Infrastructure | Operating | Scenario Plan |  |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |  |
Approved regulated return on equity |  | 9.90% |  |  |  |  |  |  |

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