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.

No definition available.

+ Details

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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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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount for the individual regulatory liability as itemized in a table of regulatory liabilities 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 405
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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- Details

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Financial instruments - Impact of Change in Fair Value of Natural Gas Derivative Contracts (Detail) CAD in Thousands, $ in Thousands	Dec. 31, 2017 CAD	Dec. 31, 2017 USD ($)	Dec. 31, 2016 CAD	Dec. 31, 2016 USD ($)
Derivative [Line Items]
Regulatory assets, natural gas derivative contracts \| CAD	CAD 551,134		CAD 291,964
Regulatory liabilities, natural gas derivative contracts \| CAD	CAD 725,056		CAD 182,734
Swap
Derivative [Line Items]
Regulatory assets, natural gas derivative contracts		$ 0		$ 0
Regulatory liabilities, natural gas derivative contracts		287		175
Options
Derivative [Line Items]
Regulatory assets, natural gas derivative contracts		0		27
Regulatory liabilities, natural gas derivative contracts		138		92
Forward contracts
Derivative [Line Items]
Regulatory assets, natural gas derivative contracts		6,319		0
Regulatory liabilities, natural gas derivative contracts		$ 20,909		$ 0