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Derivatives Instruments (Concentration Risk) (Details) - CAD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ (1,056) | $ (1,119)
% of total exposure | (100.00%) | (100.00%)
Derivative Instruments (current and long-term) |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ (98) | $ (87)
% of total exposure | (9.00%) | (8.00%)
Credit Concentration Risk |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ (805) | $ (860)
Credit rating of A- or above | Derivative Instruments (current and long-term) |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ (60) | $ (47)
% of total exposure | (6.00%) | (4.00%)
Credit rating of BBB- to BBB+ | Derivative Instruments (current and long-term) |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ (13) | $ (8)
% of total exposure | (1.00%) | (1.00%)
Not rated | Derivative Instruments (current and long-term) |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ (25) | $ (32)
% of total exposure | (2.00%) | (3.00%)
Receivables, net |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ (958) | $ (1,032)
% of total exposure | (91.00%) | (92.00%)
Receivables, net | Classification as assets held for sale |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ 0 | $ (55)
% of total exposure | 0.00% | (5.00%)
Receivables, net | Other accounts receivable |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ (159) | $ (184)
% of total exposure | (15.00%) | (16.00%)
Receivables, net | Trading group |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ (170) | $ (192)
% of total exposure | (16.00%) | (17.00%)
Receivables, net | Credit rating of A- or above | Trading group |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ (54) | $ (38)
% of total exposure | (5.00%) | (3.00%)
Receivables, net | Credit rating of BBB- to BBB+ | Trading group |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ (41) | $ (59)
% of total exposure | (4.00%) | (5.00%)
Receivables, net | Credit rating of CCC- to CCC+ | Trading group |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ 0 | $ 0
% of total exposure | 0.00% | 0.00%
Receivables, net | Not rated | Trading group |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ (75) | $ (95)
% of total exposure | (7.00%) | (9.00%)
Regulated utilities | Receivables, net |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ (629) | $ (711)
% of total exposure | (60.00%) | (64.00%)
Regulated utilities | Receivables, net | Residential |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ (341) | $ (344)
% of total exposure | (32.00%) | (31.00%)
Regulated utilities | Receivables, net | Commercial |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ (143) | $ (170)
% of total exposure | (14.00%) | (15.00%)
Regulated utilities | Receivables, net | Industrial |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ (49) | $ (66)
% of total exposure | (5.00%) | (6.00%)
Regulated utilities | Receivables, net | Other |  |
Concentration Risk [Line Items] |  |
Concentration Risk, maximum exposure | $ (96) | $ (131)
% of total exposure | (9.00%) | (12.00%)

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- Definition Maximum amount of loss due to credit risk that, based on the gross fair value of the financial instrument, the entity would incur if parties to the financial instruments that make up the concentration failed completely to perform according to the terms of the contracts and the collateral or other security, if any, for the amount due proved to be of no value to the entity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13537-108611 + Details
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