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Regulatory Assets and Liabilities (ROE of NSPI) (Details) - CAD CAD in Millions |  | 12 Months Ended |
--- | --- | --- | ---
Jul. 19, 2016 | Dec. 31, 2016 | Dec. 31, 2015
Public Utilities, General Disclosures [Line Items] |  |  |
Regulatory Liabilities |  | CAD 1,639.0 | CAD 465.0
Regulatory Assets |  | 1,322.0 | 699.0
Fuel Adjustment Mechanism Asset [Member] |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Regulatory Assets |  | CAD 0.0 | CAD 14.0
Nova Scotia Power Inc. [Member] | Fuel Adjustment Mechanism Asset [Member] |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Regulated common equity component |  | 40.00% |
Approved average annual increase |  | (1.00%) |
Public Utilities Prior Recovery of Prior Period Fuel Costs |  | CAD 12.0 |
Public Utilties Additional Contribution To Customers |  | 0.2 |
Nova Scotia Power Inc. [Member] | Fuel Adjustment Mechanism [Member] |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Public Utilities Prior Recovery of Prior Period Fuel Costs |  | 3.0 |
Public Utilties Fuel Costs Savings Achieved During the Period |  | 2.8 |
Public Utilities refunds payable to customers |  | CAD 36.0 |
Nova Scotia Power Inc. [Member] | Rate Stability Plan fuel costs for 2017 through 2019 [Member] | Fuel Adjustment Mechanism Asset [Member] |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Approved average annual increase | 1.10% |  |
Nova Scotia Power Inc. [Member] | Minimum [Member] | Fuel Adjustment Mechanism Asset [Member] |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Public Utilities, Approved Return on Equity, Percentage |  | 8.75% |
Nova Scotia Power Inc. [Member] | Maximum [Member] | Fuel Adjustment Mechanism Asset [Member] |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |
Public Utilities, Approved Return on Equity, Percentage |  | 9.25% |

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- Definition The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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