Represents the percentage of return on equity approved by National Energy Board (NEB).

No definition available.

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Period Type:	duration

- Definition

Represents the percentage of deemed common equity required for approving ROE by the National Energy Board (NEB).

+ References

No definition available.

+ Details

Name:	trp_DeemedCommonEquityPercentage
Namespace Prefix:	trp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Fixed Toll Term, Period

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Payment to Reduce Revenue Requirement, Net of Tax

+ References

No definition available.

+ Details

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Namespace Prefix:	trp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Public Utilities, Period of Settlement

+ References

No definition available.

+ Details

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Balance Type:	na
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- Definition

Public Utilities, Rate Matters, Term of Regulatory Decision

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

17bc34ec-53cd-11e3-b035-22000a1e8102

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Total increase in earnings in the period representing the cost of equity (based on assumed rate of return) and/or borrowed funds (based on interest rate) used to finance construction of regulated assets, which is expected to be recovered through rate adjustments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44278-110382

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 360
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6500269&loc=d3e45485-110386

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage of public utility's approved rate increase (decrease) by regulatory agency.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesApprovedRateIncreaseDecreasePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Composite depreciation rate for public utility plants in service.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	trp_TransmissionSystemsAxis=trp_CanadianMainlineMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=country_CA
Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProjectAxis=trp_NGTLSystemMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RegulatoryAgencyAxis=trp_NationalEnergyBoardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=trp_A2015RevenueRequirementSettlementMember
Namespace Prefix:
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RATE-REGULATED BUSINESSES - Narrative (Details) - CAD CAD in Millions			1 Months Ended			12 Months Ended			24 Months Ended	48 Months Ended
	Jul. 01, 2015	Nov. 28, 2014	Feb. 28, 2015	Nov. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2021	Dec. 31, 2019
Rate-regulated business
Allowance for funds used during construction						CAD 295	CAD 136	CAD 37
Settlement, reduction in rates	3.00%
Scenario, forecast
Rate-regulated business
Settlement, reduction in rates									8.00%	10.00%
Canadian Mainline \| Canadian Regulated Operations
Rate-regulated business
Approved ROE on deemed common equity		10.10%			11.50%
Deemed common equity		40.00%			40.00%
Term of regulatory decision					5 years			5 years
After-tax annual contribution to reduce revenue requirement		CAD 20
Fixed toll term		6 years
NGTL System \| National Energy Board \| 2015 Revenue Requirement Settlement
Rate-regulated business
Approved ROE on deemed common equity			10.10%
Deemed common equity			40.00%
Period of settlement			1 year
Composite depreciation rate							3.12%
NGTL System \| National Energy Board \| 2015 Revenue Requirement Settlement \| Canadian Regulated Operations
Rate-regulated business
Approved ROE on deemed common equity				10.10%
Deemed common equity				40.00%