COMPONENTS OF ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Changes in AOCI
Balance at beginning of year	$ 63,398	$ 63,368
Other comprehensive income/(loss) retained in AOCI	(1,144)	4,816	$ 298
Other		16	0
Other comprehensive (income)/loss reclassified to earnings	(1,187)	5,004	564
Income tax on amounts retained in AOCI	(33)	(349)	(187)
Income tax on amounts reclassified to earnings	3	(39)	(72)
Tax impact	(30)	(388)	(259)
Balance at end of year	64,483	63,398	63,368
Interest rate contracts
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs	28	186	296
Commodity contracts
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs			1
Foreign exchange contracts
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs	(47)	(4)	5
Other contracts
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs		4	2
Equity investment disposal
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs			(66)
Total
Changes in AOCI
Balance at beginning of year	3,520	(1,096)	(1,401)
Balance at end of year	2,303	3,520	(1,096)
Cash Flow Hedges
Changes in AOCI
Balance at beginning of year	121	(897)	(1,326)
Other comprehensive income/(loss) retained in AOCI	232	1,125	238
Other		0	17
Other comprehensive (income)/loss reclassified to earnings	260	1,311	559
Income tax on amounts retained in AOCI	(47)	(250)	(61)
Income tax on amounts reclassified to earnings	(14)	(43)	(69)
Tax impact	(61)	(293)	(130)
Balance at end of year	320	121	(897)
Cash Flow Hedges | Interest rate contracts
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs	28	186	296
Cash Flow Hedges | Commodity contracts
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs			1
Cash Flow Hedges | Foreign exchange contracts
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs	0	(4)	5
Cash Flow Hedges | Other contracts
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs		4	2
Excluded Components of Fair Value Hedges
Changes in AOCI
Balance at beginning of year	(35)	0	5
Other comprehensive income/(loss) retained in AOCI	62	(35)	(5)
Other comprehensive (income)/loss reclassified to earnings	15	(35)	(5)
Income tax on amounts retained in AOCI	(14)
Income tax on amounts reclassified to earnings	11
Tax impact	(3)	0	0
Balance at end of year	(23)	(35)	0
Excluded Components of Fair Value Hedges | Foreign exchange contracts
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs	(47)
Net Investment Hedges
Changes in AOCI
Balance at beginning of year	(1,137)	(166)	(215)
Other comprehensive income/(loss) retained in AOCI	409	(971)	49
Other comprehensive (income)/loss reclassified to earnings	409	(971)	49
Income tax on amounts retained in AOCI	0
Income tax on amounts reclassified to earnings	0
Tax impact	0	0	0
Balance at end of year	(728)	(1,137)	(166)
Cumulative Translation Adjustment
Changes in AOCI
Balance at beginning of year	4,348	56	568
Other comprehensive income/(loss) retained in AOCI	(1,695)	4,292	(492)
Other		0	(20)
Other comprehensive (income)/loss reclassified to earnings	(1,695)	4,292	(512)
Income tax on amounts retained in AOCI	0
Income tax on amounts reclassified to earnings	0
Tax impact	0	0
Balance at end of year	2,653	4,348	56
Equity Investees
Changes in AOCI
Balance at beginning of year	5	(5)	66
Other comprehensive income/(loss) retained in AOCI	6	(6)	(12)
Other		16	3
Other comprehensive (income)/loss reclassified to earnings	6	10	(75)
Income tax on amounts retained in AOCI	0
Income tax on amounts reclassified to earnings	0		4
Tax impact	0	0	4
Balance at end of year	11	5	(5)
Equity Investees | Equity investment disposal
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs			(66)
Pension and OPEB Adjustment
Changes in AOCI
Balance at beginning of year	218	(84)	(499)
Other comprehensive income/(loss) retained in AOCI	(158)	411	520
Amortization of pension and OPEB actuarial loss and prior service costs	(24)	(14)	28
Other comprehensive (income)/loss reclassified to earnings	(182)	397	548
Income tax on amounts retained in AOCI	28	(99)	(126)
Income tax on amounts reclassified to earnings	6	4	(7)
Tax impact	34	(95)	(133)
Balance at end of year	$ 70	$ 218	$ (84)