COMPONENTS OF ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) - CAD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Changes in AOCI
Balance at the beginning of the period	$ 69,407
Other comprehensive income/(loss) retained in AOCI	851	$ (2,483)
Other comprehensive (income)/loss reclassified to earnings	13	59
Total before tax impact	1,044	(2,316)
Income tax on amounts retained in AOCI	172	227
Income tax on amounts reclassified to earnings	(45)	(49)
Tax impact	127	178
Other		48
Balance at the end of the period	68,435	72,676
Interest rate contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	179	108
Commodity contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	(1)
Foreign exchange contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	3	4
Other contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	(1)	(4)
Total
Changes in AOCI
Balance at the beginning of the period	(272)	2,672
Balance at the end of the period	899	582
Cash Flow  Hedges
Changes in AOCI
Balance at the beginning of the period	(1,073)	(770)
Other comprehensive income/(loss) retained in AOCI	(696)	(845)
Total before tax impact	(516)	(737)
Income tax on amounts retained in AOCI	167	254
Income tax on amounts reclassified to earnings	(42)	(34)
Tax impact	125	220
Other		0
Balance at the end of the period	(1,464)	(1,287)
Cash Flow  Hedges | Interest rate contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	179	108
Cash Flow  Hedges | Commodity contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	(1)
Cash Flow  Hedges | Foreign exchange contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	3	4
Cash Flow  Hedges | Other contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	(1)	(4)
Excluded Components of Fair Value Hedges
Changes in AOCI
Balance at the beginning of the period	0
Other comprehensive income/(loss) retained in AOCI	7
Total before tax impact	7
Income tax on amounts retained in AOCI	0
Income tax on amounts reclassified to earnings	0
Tax impact	0
Balance at the end of the period	7
Net Investment Hedges
Changes in AOCI
Balance at the beginning of the period	(317)	(598)
Other comprehensive income/(loss) retained in AOCI	(228)	167
Total before tax impact	(228)	167
Income tax on amounts retained in AOCI	7	(20)
Income tax on amounts reclassified to earnings	0	0
Tax impact	7	(20)
Other		0
Balance at the end of the period	(538)	(451)
Cumulative Translation Adjustment
Changes in AOCI
Balance at the beginning of the period	1,396	4,323
Other comprehensive income/(loss) retained in AOCI	1,760	(1,831)
Total before tax impact	1,760	(1,831)
Income tax on amounts retained in AOCI	0	0
Income tax on amounts reclassified to earnings	0	0
Tax impact	0	0
Other		0
Balance at the end of the period	3,156	2,492
Equity Investees
Changes in AOCI
Balance at the beginning of the period	67	34
Other comprehensive income/(loss) retained in AOCI	8	26
Total before tax impact	8	26
Income tax on amounts retained in AOCI	(2)	(7)
Income tax on amounts reclassified to earnings	0	0
Tax impact	(2)	(7)
Other		(7)
Balance at the end of the period	73	46
Pension and OPEB Adjustment
Changes in AOCI
Balance at the beginning of the period	(345)	(317)
Other comprehensive (income)/loss reclassified to earnings	13	59
Total before tax impact	13	59
Income tax on amounts retained in AOCI	0	0
Income tax on amounts reclassified to earnings	(3)	(15)
Tax impact	(3)	(15)
Other		55
Balance at the end of the period	$ (335)	$ (218)