OTHER COMPREHENSIVE INCOME/(LOSS) AND ACCUMULATED OTHER COMPREHENSIVE LOSS - Reconciliation (Details) - CAD CAD in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI Balance	CAD (1,235)	CAD (934)	CAD (1,448)
Other comprehensive income/(loss) before reclassifications	162	(266)	435
Amounts reclassified from accumulated other comprehensive loss	134	(35)	79
Net current period other comprehensive income	296	(301)	514
AOCI Balance	(939)	(1,235)	(934)
Other comprehensive income/(loss) before reclassifications attributable to noncontrolling interest	306	130	66
Cash flow hedge losses expected to be reclassified within the next twelve months, before tax	83
Cash flow hedge losses expected to be reclassified within the next twelve months, net of tax	51
Currency translation adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI Balance	(518)	(629)	(707)
Other comprehensive income/(loss) before reclassifications	135	111	78
Net current period other comprehensive income	135	111	78
AOCI Balance	(383)	(518)	(629)
Cash flow hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI Balance	(128)	(4)	(116)
Other comprehensive income/(loss) before reclassifications	(57)	(69)	71
Amounts reclassified from accumulated other comprehensive loss	88	(55)	41
Net current period other comprehensive income	31	(124)	112
AOCI Balance	(97)	(128)	(4)
Pension and OPEB plan adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI Balance	(281)	(197)	(287)
Other comprehensive income/(loss) before reclassifications	51	(102)	67
Amounts reclassified from accumulated other comprehensive loss	32	18	23
Net current period other comprehensive income	83	(84)	90
AOCI Balance	(198)	(281)	(197)
Equity Investments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI Balance	(308)	(104)	(338)
Other comprehensive income/(loss) before reclassifications	33	(206)	219
Amounts reclassified from accumulated other comprehensive loss	14	2	15
Net current period other comprehensive income	47	(204)	234
AOCI Balance	CAD (261)	CAD (308)	CAD (104)

Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months, before Tax

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- Definition

Other Comprehensive Income (Loss), before Reclassifications, Net of Tax, Portion Attributable to Noncontrolling Interest

+ References

No definition available.

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Other Comprehensive Income (Loss), before Reclassifications, Net of Tax, Portion Attributable to Parent

+ References

No definition available.

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Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax, Portion Attributable to Parent

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No definition available.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e637-108580

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-Publisher FASB
-Name Accounting Standards Codification
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-Section 45
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e681-108580

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Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 31
-Article 5

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
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The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 30
-Section 50
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80748-113994

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
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