COMPONENTS OF ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) - CAD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Changes in AOCI
Balance at the beginning of the period	$ 69,407
Other comprehensive income/(loss) retained in AOCI	1,763	$ (2,852)
Other comprehensive (income)/loss reclassified to earnings	9	57
Total before tax impact	1,877	(2,724)
Income tax on amounts retained in AOCI	175	160
Income tax on amounts reclassified to earnings	(27)	(39)
Tax impact	148	121
Other		55
Balance at the end of the period	69,941	72,805
Interest rate contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	103	72
Foreign exchange contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	2	2
Other contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings		(3)
Total
Changes in AOCI
Balance at the beginning of the period	(272)	2,672
Balance at the end of the period	1,753	124
Cash Flow Hedges
Changes in AOCI
Balance at the beginning of the period	(1,073)	(770)
Other comprehensive income/(loss) retained in AOCI	(738)	(618)
Total before tax impact	(633)	(547)
Income tax on amounts retained in AOCI	180	196
Income tax on amounts reclassified to earnings	(25)	(25)
Tax impact	155	171
Balance at the end of the period	(1,551)	(1,146)
Cash Flow Hedges | Interest rate contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	103	72
Cash Flow Hedges | Foreign exchange contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	2	2
Cash Flow Hedges | Other contracts
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings		(3)
Excluded Components of Fair Value Hedges
Changes in AOCI
Balance at the beginning of the period	0
Other comprehensive income/(loss) retained in AOCI	8
Total before tax impact	8
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	8
Net Investment Hedges
Changes in AOCI
Balance at the beginning of the period	(317)	(598)
Other comprehensive income/(loss) retained in AOCI	(375)	252
Total before tax impact	(375)	252
Income tax on amounts retained in AOCI	0	(31)
Income tax on amounts reclassified to earnings	0	0
Tax impact	0	(31)
Balance at the end of the period	(692)	(377)
Cumulative Translation Adjustment
Changes in AOCI
Balance at the beginning of the period	1,396	4,323
Other comprehensive income/(loss) retained in AOCI	2,843	(2,508)
Total before tax impact	2,843	(2,508)
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	4,239	1,815
Equity Investees
Changes in AOCI
Balance at the beginning of the period	67	34
Other comprehensive income/(loss) retained in AOCI	25	22
Total before tax impact	25	22
Income tax on amounts retained in AOCI	(5)	(5)
Income tax on amounts reclassified to earnings	0	0
Tax impact	(5)	(5)
Balance at the end of the period	87	51
Pension and OPEB Adjustment
Changes in AOCI
Balance at the beginning of the period	(345)	(317)
Other comprehensive (income)/loss reclassified to earnings	9	57
Total before tax impact	9	57
Income tax on amounts retained in AOCI	0	0
Income tax on amounts reclassified to earnings	(2)	(14)
Tax impact	(2)	(14)
Other		55
Balance at the end of the period	$ (338)	$ (219)