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Accounts Receivable and Other Current Assets - Narrative (Details) CAD in Millions, $ in Millions	Dec. 31, 2016 CAD	Dec. 31, 2015 CAD	Apr. 30, 2015 USD ($)	Apr. 30, 2015 CAD
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets held for sale	CAD 0	CAD 38
UNS Energy
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets held for sale			$ 21	CAD 29
Interest for sale (percentage)		17.05%
Walden Hydroelectric Power Plant Assets | NON-REGULATED
Accounts, Notes, Loans and Financing Receivable [Line Items]
Assets held for sale		CAD 9

X

- Definition

Jointly Owned Utility Plant, Proportionate Ownership Share, Available For Sale

+ References

No definition available.

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- Definition

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.

+ References

No definition available.

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- Definition

Amount of assets held-for-sale that are not part of a disposal group, expected to be sold within a year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 15
-Paragraph 4
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=6390208&loc=d3e400-110220

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- Details

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