COMPONENTS OF ACCUMULATED OTHER COMPREHENSIVE INCOME/(LOSS) (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Components of accumulated other comprehensive loss
Balance at beginning of year	$ 64,363	$ 69,407
Other comprehensive income/(loss) retained in AOCI	298	(1,522)	$ (3,296)
Changes in AOCI
Other	0		48
Other comprehensive (income)/loss reclassified to earnings	564	(1,249)	(3,121)
Income tax on amounts retained in AOCI	(187)	182	164
Income tax on amounts reclassified to earnings	(72)	(62)	(35)
Tax impact	(259)	120	129
Balance at end of year	63,368	64,363	69,407
Interest rate contracts
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs	296	253	157
Commodity contracts
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs	1		(1)
Forward exchange contracts
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs	5	5	5
Other contracts
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs	2	(2)	(3)
Equity investment disposal
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs	0
Cash Flow Hedges
Components of accumulated other comprehensive loss
Balance at beginning of year	(1,326)	(1,073)	(770)
Other comprehensive income/(loss) retained in AOCI	238	(591)	(599)
Changes in AOCI
Other	17		0
Other comprehensive (income)/loss reclassified to earnings	559	(335)	(441)
Income tax on amounts retained in AOCI	(61)	140	169
Income tax on amounts reclassified to earnings	(69)	(58)	(31)
Tax impact	(130)	82	138
Balance at end of year	(897)	(1,326)	(1,073)
Cash Flow Hedges | Interest rate contracts
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs	296	253	157
Cash Flow Hedges | Commodity contracts
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs	1		(1)
Cash Flow Hedges | Forward exchange contracts
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs	5	5	5
Cash Flow Hedges | Other contracts
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs	2	(2)	(3)
Excluded Components of Fair Value Hedges
Components of accumulated other comprehensive loss
Balance at beginning of year	5	0
Other comprehensive income/(loss) retained in AOCI	(5)	5
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	(5)	5
Income tax on amounts retained in AOCI	0	0
Income tax on amounts reclassified to earnings	0	0
Tax impact	0	0
Balance at end of year	0	5	0
Net Investment Hedges
Components of accumulated other comprehensive loss
Balance at beginning of year	(215)	(317)	(598)
Other comprehensive income/(loss) retained in AOCI	49	115	320
Changes in AOCI
Other comprehensive (income)/loss reclassified to earnings	49	115	320
Income tax on amounts retained in AOCI	0	(13)	(39)
Income tax on amounts reclassified to earnings	0	0
Tax impact	0	(13)	(39)
Balance at end of year	(166)	(215)	(317)
Cumulative Translation Adjustment
Components of accumulated other comprehensive loss
Balance at beginning of year	568	1,396	4,323
Other comprehensive income/(loss) retained in AOCI	(492)	(828)	(2,927)
Changes in AOCI
Other	(20)		0
Other comprehensive (income)/loss reclassified to earnings	(512)	(828)	(2,927)
Income tax on amounts retained in AOCI	0	0
Income tax on amounts reclassified to earnings	0	0
Tax impact	0	0
Balance at end of year	56	568	1,396
Equity Investees
Components of accumulated other comprehensive loss
Balance at beginning of year	66	67	34
Other comprehensive income/(loss) retained in AOCI	(12)	(2)	34
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs	66
Other	3		(7)
Other comprehensive (income)/loss reclassified to earnings	(75)	(2)	34
Income tax on amounts retained in AOCI	0	1	6
Income tax on amounts reclassified to earnings	4	0
Tax impact	4	1	6
Balance at end of year	(5)	66	67
Pension and OPEB Adjustment
Components of accumulated other comprehensive loss
Balance at beginning of year	(499)	(345)	(317)
Other comprehensive income/(loss) retained in AOCI	520	(221)	(124)
Changes in AOCI
Amortization of pension and OPEB actuarial loss and prior service costs	28	17	17
Other			55
Other comprehensive (income)/loss reclassified to earnings	548	(204)	(107)
Income tax on amounts retained in AOCI	(126)	54	28
Income tax on amounts reclassified to earnings	(7)	(4)	(4)
Tax impact	(133)	50	24
Balance at end of year	(84)	(499)	(345)
Total
Components of accumulated other comprehensive loss
Balance at beginning of year	(1,401)	(272)	2,672
Changes in AOCI
Balance at end of year	$ (1,096)	$ (1,401)	$ (272)