INCOME TAXES - COMPONENTS (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings/(loss) before income taxes and discontinued operations
Earnings before income taxes	$ 4,190	$ 7,535	$ 3,570
Current income taxes
Total current income taxes	327	552	385
Deferred income taxes
Total deferred income taxes	447	1,156	(148)
Income tax expense	774	1,708	237
Canada
Earnings/(loss) before income taxes and discontinued operations
Domestic	2,789	3,560	118
Current income taxes
Domestic	165	347	311
Deferred income taxes
Domestic	378	490	(598)
US
Earnings/(loss) before income taxes and discontinued operations
Foreign	407	3,115	2,582
Current income taxes
Foreign	64	107	66
Deferred income taxes
Foreign	66	672	439
Other
Earnings/(loss) before income taxes and discontinued operations
Foreign	994	860	870
Current income taxes
Foreign	98	98	8
Deferred income taxes
Foreign	$ 3	$ (6)	$ 11