INCOME TAXES - COMPONENTS (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings/(loss) before income taxes and discontinued operations
Earnings before income taxes	$ 7,535	$ 3,570	$ 569
Current income taxes
Total current income taxes	552	385	180
Deferred income taxes
Total deferred income taxes	1,156	(148)	(2,877)
Income tax (recovery)/expense	1,708	237	(2,697)
Canada
Earnings/(loss) before income taxes and discontinued operations
Domestic	3,560	118	2,200
Current income taxes
Domestic	347	311	129
Deferred income taxes
Domestic	490	(598)	299
United States
Earnings/(loss) before income taxes and discontinued operations
Foreign	3,115	2,582	(2,431)
Current income taxes
Foreign	107	66	46
Deferred income taxes
Foreign	672	439	(3,160)
Other
Earnings/(loss) before income taxes and discontinued operations
Foreign	860	870	800
Current income taxes
Foreign	98	8	5
Deferred income taxes
Foreign	$ (6)	$ 11	$ (16)