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Commitments and Contingencies (Collaborative Arrangements) (Details) - Jointly Owned Electricity Generation Plant - NSPI - CAD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] |  |
Regulated fuel for generation and purchased power | $ 19 | $ 19
Operating, maintenance and general (OM&G) | $ 3 | $ 3

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- Definition Amount of operating expense for routine plant maintenance, repairs and operations of regulated operation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.2(b)) -URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227 + Details
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