Number of shares of equity interest issued or to be issued for each outstanding share of common stock of the acquiree.

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The pro forma earnings before interest and income taxes for the period as if the business combination or combinations had been completed at the beginning of a period.

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No definition available.

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This element represents the amount of earnings before interest and income taxes of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

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Amount of direct costs of the business combination including legal, accounting, and other costs incurred to consummate the business acquisition.

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Number of shares of equity interests issued or issuable to acquire entity.

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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.

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Percentage of voting equity interests acquired at the acquisition date in the business combination.

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Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination.

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No definition available.

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

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This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Amount of equity interests of the acquirer, including instruments or interests issued or issuable in consideration for the business combination.

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This element represents the amount of earnings or loss of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

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This element represents the amount of revenue of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

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Number of reporting units tested for impairment of goodwill. A reporting unit is an operating segment or one level below an operating segment.

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The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

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The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

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ACQUISITIONS AND DISPOSITIONS - Acquisitions (Narrative) (Details) $ in Millions			9 Months Ended	10 Months Ended	12 Months Ended
	Feb. 27, 2017 CAD ($) shares	Apr. 01, 2016 CAD ($)	Dec. 31, 2016 CAD ($)	Dec. 31, 2017 CAD ($)	Dec. 31, 2018 CAD ($) reporting_unit	Dec. 31, 2017 CAD ($)	Dec. 31, 2016 CAD ($)	Feb. 27, 2017 $ / shares
Business Acquisition [Line Items]
Number of reporting units \| reporting_unit					2
Cash consideration					$ 0	$ 0	$ 644
Spectra Energy
Business Acquisition [Line Items]
Purchase price	$ 37,509
Shares paid to acquiree for each share of acquiree stock (in shares) \| shares	0.984
Ownership interest acquired (as a percent)								100.00%
Cash paid in lieu of fractional shares	$ 3
Acquisition-related expenses/transaction costs incurred					$ 231
Costs incurred						180	51
Revenues generated by acquiree				$ 5,740
Earnings generated by acquiree				$ 2,574
Cash consideration	$ 3
Pro forma revenues						$ 45,669	40,934
Tupper Main and Tupper West
Business Acquisition [Line Items]
Acquisition-related expenses/transaction costs incurred		$ 1
Revenues generated by acquiree			$ 33
Cash consideration		$ 539
Earnings before interest and income taxes of acquiree			$ 22
Pro forma revenues							44
Pro forma earnings before interest and income taxes							$ 28
Common shares \| Spectra Energy
Business Acquisition [Line Items]
Shares paid as consideration (in shares) \| shares	691,000,000
Share price (in USD per share) \| $ / shares								$ 41.34
Value of shares issued	$ 37,429
Share options \| Spectra Energy
Business Acquisition [Line Items]
Shares paid as consideration (in shares) \| shares	3,500,000
Value of shares issued	$ 77
Gas Transmission and Midstream
Business Acquisition [Line Items]
Number of reporting units \| reporting_unit					2