DESCRIPTION OF TCPL'S BUSINESS (Details)	12 Months Ended
Dec. 31, 2016 plant segment core_business mi km Bcf
Segment Reporting Information [Line Items]
Number of core businesses \| core_business	3
Number of business segments in which the entity operates \| segment	6
Canadian Natural Gas Pipelines
Segment Reporting Information [Line Items]
Investments of regulated natural gas pipelines (in kilometers) \| km	40,111
Investments of regulated natural gas pipelines (in miles) \| mi	24,923
U.S. Natural Gas Pipelines
Segment Reporting Information [Line Items]
Investments of regulated natural gas pipelines (in kilometers) \| km	49,776
Investments of regulated natural gas pipelines (in miles) \| mi	30,933
Investments of regulated natural gas storage facilities (in billion cubic feet) \| Bcf	535
Mexico Natural Gas Pipelines
Segment Reporting Information [Line Items]
Investments of regulated natural gas pipelines (in kilometers) \| km	1,617
Investments of regulated natural gas pipelines (in miles) \| mi	1,005
Liquids Pipelines
Segment Reporting Information [Line Items]
Wholly owned and operated crude oil pipeline systems (in kilometers) \| km	4,324
Wholly owned and operated crude oil pipeline systems (in miles) \| mi	2,687
Energy
Segment Reporting Information [Line Items]
Number of electrical power generation plants \| plant	18
Non-regulated natural gas storage facilities (in billion cubic feet) \| Bcf	118
Held-for-sale \| Energy
Segment Reporting Information [Line Items]
Number of electrical power generation plants \| plant	5
Millennium Pipeline \| U.S. Natural Gas Pipelines
Segment Reporting Information [Line Items]
Jointly owned utility plant, proportionate ownership share, percent	47.50%
Pennant Midstream \| U.S. Natural Gas Pipelines
Segment Reporting Information [Line Items]
Jointly owned utility plant, proportionate ownership share, percent	47.00%
TransGas Pipeline Columbia \| Mexico Natural Gas Pipelines
Segment Reporting Information [Line Items]
Jointly owned utility plant, proportionate ownership share, percent	46.50%

Public Utilities, Property, Plant and Equipment, Liquids Pipelines, in Kilometers

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Public Utilities, Property, Plant and Equipment, Liquids Pipelines, in Miles

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Public Utilities, Property, Plant and Equipment, Non-Regulated Natural Gas Storage Facilities, in Billion Cubic Feet

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Public Utilities, Property, Plant and Equipment, Number of Electrical Power Generation Plants

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Public Utilities, Property, Plant and Equipment, Regulated Natural Gas Pipelines, in Kilometers

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Public Utilities, Property, Plant and Equipment, Regulated Natural Gas Pipelines, in Miles

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Public Utilities, Property, Plant and Equipment, Regulated Natural Gas Storage Facilities, in Billion Cubic Feet

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- Definition

Segment Reporting, Number of Core Businesses

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- Definition

The proportionate share of interest (percent) in a jointly owned utility plant.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 360
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 10.C)
-URI http://asc.fasb.org/extlink&oid=6500719&loc=d3e659983-123033

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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