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.

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Carrying amount as of the balance sheet date of capitalized costs of a regulated entity, consisting of the planning, implementing, and monitoring activities which are designed to encourage consumers to modify their level and pattern of energy usage, which are expected to be recoverable through rate adjustments after one year or beyond the normal operating cycle, if longer.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Amount of loss (recovery of loss) related to a plant abandonment.

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Describes the continual or periodic assessment of the probability of future recovery of regulatory assets.

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Remaining recovery period of regulatory assets for which no return on investment during recovery period is provided, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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A noncash adjustment to the provision established for storm damage by an oil, gas, or utility company.

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Regulatory Assets and Liabilities - Assets and Liabilities (Narrative) (Details) $ in Millions, $ in Millions	1 Months Ended		12 Months Ended
	Jan. 31, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 CAD ($)	Dec. 31, 2019 CAD ($)	Dec. 31, 2017 CAD ($)	Dec. 31, 2016 CAD ($)	Dec. 31, 2015 CAD ($)
GBPC \| Hurricane \| Loss from Catastrophes
Public Utilities, General Disclosures [Line Items]
Storm cost	$ 15
Storm Reserve				$ 18
Recovery Period			5 years
GBPC \| Steam turbine
Public Utilities, General Disclosures [Line Items]
Public Utilities, Property, Plant and Equipment, Amount of Loss (Recovery) on Plant Abandonment			$ 21
NSPI
Public Utilities, General Disclosures [Line Items]
Recovery Period			3 years
Regulatory Asset Recovery Assessments			As approved on December 6, 2019 as part of NSPI’s three-year Fuel Stability Plan, differences between actual fuel costs and fuel revenues recovered from customers for the years 2020 to 2022, will be recovered or returned to customers after 2022. The UARB’s decision to approve the Fuel Stability Plan directed that any annual non-fuel revenues above NSPI’s approved range of ROE are to be applied to the FAM.
NSPI \| Renewable Energy Program
Public Utilities, General Disclosures [Line Items]
Recovery Period			8 years
Regulatory Asset Recovery Assessments			The Nova Scotia Utility and Review Board (“UARB”) approved implementation of the 2015 DSM deferral set at $35 million in 2015 and recoverable from customers over an 8-year period beginning in 2016.
Replacement program						$ 2	$ 31	$ 35
NSPI \| Unamortized defeasance costs \| Defeased debt
Public Utilities, General Disclosures [Line Items]
Long-term debt				$ 582	$ 740
Tampa Electric \| Hurricane
Public Utilities, General Disclosures [Line Items]
Storm cost		$ 8