DEBT - Narrative (Details) $ in Millions		3 Months Ended
	Apr. 15, 2023 USD ($)	Mar. 31, 2023 CAD ($)	Feb. 28, 2023 CAD ($)	Dec. 31, 2022 CAD ($)
Line of Credit Facility [Line Items]
Commitment fee percentage		0.10%
Long-term debt		$ 71,740,000,000		$ 72,939,000,000
Long-term debt, fair value adjustment		588,000,000		608,000,000
Amortization of fair value adjustment		11,000,000
Commercial paper and credit facility draws
Line of Credit Facility [Line Items]
Long-term debt		9,000,000,000		10,500,000,000
Fixed-to-floating subordinated term notes | Subordinated term notes
Line of Credit Facility [Line Items]
Subordinated debt		10,300,000,000
Five-year Callable Fixed To Floating Rate Subordinated Notes | Subsequent event | Long-Term Debt
Line of Credit Facility [Line Items]
Long-term debt, amount outstanding	$ 600
Interest rate (as a percent)	6.38%
Revolving credit facility | 364-day extendible credit facility
Line of Credit Facility [Line Items]
Amount of credit facility		2,500,000,000	$ 2,000,000,000
Uncommitted demand credit facilities
Line of Credit Facility [Line Items]
Amount of credit facility		1,300,000,000		1,300,000,000
Unutilized amount of facility		$ 720,000,000		$ 689,000,000