Non-cash operating items - Changes in Non-Cash Operating Items (Detail) - CAD CAD in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Disclosure Changes In Non Cash Operating Items [Abstract]
Accounts receivable	CAD (18,502)	CAD 6,612
Fuel and natural gas in storage	(1,970)	6,877
Supplies and consumable inventory	1,392	692
Income taxes receivable	1,674	145
Prepaid expenses	(897)	(6,161)
Accounts payable	(23,178)	24,524
Accrued liabilities	25,122	(9,454)
Current income tax liability	(3,432)	(4,552)
Net regulatory assets and liabilities	(54,235)	(14,979)
Changes in non-cash operating items	CAD (74,026)	CAD 3,704

Disclosure - Changes in Non-Cash Operating Items [Abstract]

No definition available.

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- Definition

The increase (decrease) during the reporting period in the aggregate amount of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

+ Details

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- Definition

The increase (decrease) during the reporting period in amount due within one year (or one business cycle) from customers for the credit sale of goods and services.

+ References

+ Details

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- Definition

The increase (decrease) during the reporting period in the aggregate amount of expenses incurred but not yet paid.

+ References

+ Details

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- Definition

The increase (decrease) during the reporting period in the value of fuel held in inventory.

+ References

+ Details

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- Definition

The increase (decrease) during the reporting period in the amounts payable to taxing authorities for taxes that are based on the reporting entity's earnings, net of amounts receivable from taxing authorities for refunds of overpayments or recoveries of income taxes, and in deferred and other tax liabilities and assets.

+ References

No definition available.

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- Definition

The increase (decrease) during the reporting period in income taxes receivable, which represents the amount due from tax authorities for refunds of overpayments or recoveries of income taxes paid.

+ References

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- Definition

The increase (decrease) during the period in the carrying amount of capitalized costs of materials, supplies, or both, which are not included in inventory.

+ References

No definition available.

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- Definition

The increase (decrease) during the reporting period of all assets and liabilities used in operating activities.

+ References

+ Details

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- Definition

The increase (decrease) during the reporting period in the amount of outstanding money paid in advance for goods or services that bring economic benefits for future periods.

+ References

+ Details

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- Definition

The increase (decrease) during the reporting period in the value of assets that are created when regulatory agencies permits public utilities to defer costs (revenues) to the balance sheet. This element is a the increase (decrease) of regulatory assets and liabilities combined.

+ References

+ Details

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