NONCONTROLLING INTERESTS - REDEEMABLE NONCONTROLLING INFORMATION (Details) - CAD ($)		12 Months Ended
	Mar. 20, 2019	Dec. 31, 2018	Dec. 31, 2017
REDEEMABLE NONCONTROLLING INTERESTS
Balance at beginning of year		$ 4,067,000,000	$ 3,392,000,000
Earnings attributable to redeemable noncontrolling interests		117,000,000	175,000,000
Change in unrealized loss on cash flow hedges		3,000,000	(21,000,000)
Other comprehensive loss from equity investees		14,000,000	0
Reclassification to earnings of loss on cash flow hedges		0	57,000,000
Foreign currency translation adjustments		4,000,000	(6,000,000)
Other comprehensive income/(loss)		21,000,000	30,000,000
Distributions to unitholders		(300,000,000)	(247,000,000)
Contributions from unitholders		70,000,000	1,178,000,000
Modified retrospective adoption of accounting standard		(38,000,000)	0
Dilution gain/(loss) for redeemable noncontrolling interests		76,000,000	(169,000,000)
Redemption value adjustment		456,000,000	(292,000,000)
Sponsored vehicle buy-in	$ (300,000,000)	(4,469,000,000)	0
Balance at end of year		$ 0	$ 4,067,000,000