COMPONENTS OF ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) - CAD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Changes in AOCI
Balance at the beginning of the period	$ 64,363
Other comprehensive income/(loss) retained in AOCI	(1,040)	$ 1,763
Total before tax impact	(880)	1,877
Income tax on amounts retained in AOCI	(103)	175
Income tax on amounts reclassified to earnings	(36)	(27)
Tax impact	(139)	148
Balance at the end of the period	64,896	69,941
Interest rate contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	142	103
Foreign exchange contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	3	2
Other contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	1
Total
Changes in AOCI
Balance at the beginning of the period	(1,401)	(272)
Balance at the end of the period	(2,420)	1,753
Cash Flow  Hedges
Changes in AOCI
Balance at the beginning of the period	(1,326)	(1,073)
Other comprehensive income/(loss) retained in AOCI	294	(738)
Other comprehensive (income)/loss reclassified to earnings	17
Total before tax impact	457	(633)
Income tax on amounts retained in AOCI	(75)	180
Income tax on amounts reclassified to earnings	(33)	(25)
Tax impact	(108)	155
Balance at the end of the period	(977)	(1,551)
Cash Flow  Hedges | Interest rate contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	142	103
Cash Flow  Hedges | Foreign exchange contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	3	2
Cash Flow  Hedges | Other contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	1
Excluded Components of Fair Value Hedges
Changes in AOCI
Balance at the beginning of the period	5	0
Other comprehensive income/(loss) retained in AOCI	(2)	8
Total before tax impact	(2)	8
Income tax on amounts retained in AOCI	0	0
Income tax on amounts reclassified to earnings	0	0
Tax impact	0	0
Balance at the end of the period	3	8
Net Investment Hedges
Changes in AOCI
Balance at the beginning of the period	(215)	(317)
Other comprehensive income/(loss) retained in AOCI	251	(375)
Total before tax impact	251	(375)
Income tax on amounts retained in AOCI	(29)	0
Income tax on amounts reclassified to earnings	0	0
Tax impact	(29)	0
Balance at the end of the period	7	(692)
Cumulative Translation Adjustment
Changes in AOCI
Balance at the beginning of the period	568	1,396
Other comprehensive income/(loss) retained in AOCI	(1,584)	2,843
Other comprehensive (income)/loss reclassified to earnings	(20)
Total before tax impact	(1,604)	2,843
Income tax on amounts retained in AOCI	0	0
Income tax on amounts reclassified to earnings	0	0
Tax impact	0	0
Balance at the end of the period	(1,036)	4,239
Equity Investees
Changes in AOCI
Balance at the beginning of the period	66	67
Other comprehensive income/(loss) retained in AOCI	1	25
Other comprehensive (income)/loss reclassified to earnings	3
Total before tax impact	4	25
Income tax on amounts retained in AOCI	1	(5)
Income tax on amounts reclassified to earnings	0	0
Tax impact	1	(5)
Balance at the end of the period	71	87
Pension and OPEB Adjustment
Changes in AOCI
Balance at the beginning of the period	(499)	(345)
Other comprehensive (income)/loss reclassified to earnings	14	9
Total before tax impact	14	9
Income tax on amounts retained in AOCI	0	0
Income tax on amounts reclassified to earnings	(3)	(2)
Tax impact	(3)	(2)
Balance at the end of the period	$ (488)	$ (338)