SHARE CAPITAL - Schedule of Common Shares (Details) $ / shares in Units, $ in Millions			3 Months Ended	12 Months Ended
	May 15, 2024 CAD ($)	Sep. 08, 2023 CAD ($) $ / shares shares	Jul. 31, 2024 CAD ($) $ / shares shares	Dec. 31, 2024 CAD ($) shares	Dec. 31, 2023 CAD ($) shares	Dec. 31, 2022 CAD ($) shares	Jul. 31, 2024 $ / shares
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period (in shares) | shares				2,125,000,000
Shares issued, net of issue costs (in shares) | shares				51,000,000	103,000,000	0
Shares issued, net of issue costs				$ 2,489.0	$ 4,485.0	$ 0.0
Shares issued on vesting of RSU, net of tax (in shares) | shares				1,000,000	0	0
Shares issued on vesting of RSUs, net of tax				$ 30.0	$ 12.0	$ 0.0
Balance at end of period (in shares) | shares				2,178,000,000	2,125,000,000
At-The-Market Offering
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common shares that can be sold under the ATM Program	$ 2,750.0
Sale of stock, consideration received on transaction			$ 2,500.0
Sale of stock, consideration received on transaction, net			2,480.0
Payments of stock issuance costs			$ 16.3
Public Offering Member
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Sale of stock, consideration received on transaction		$ 4,600.0
Sale of stock, number of shares issued in transaction (shares) | shares		102,913,500
Sale of stock, price per share (in Canadian dollars per share and US dollars per share) | $ / shares		$ 44.70
Common Shares
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period (in shares) | shares				2,125,000,000	2,025,000,000	2,026,000,000
Balance at beginning of period, amount				$ 69,180.0	$ 64,760.0	$ 64,799.0
Shares issued on exercise of stock options (in shares) | shares				1,000,000	0	2,000,000
Shares issued on exercise of stock options				$ 39.0	$ 3.0	$ 53.0
Share repurchases at stated value (in shares) | shares				0	(3,000,000)	(3,000,000)
Share repurchases at stated value				$ 0.0	$ (80.0)	$ (88.0)
Other ( in shares) | shares				0	0	0
Other				$ 0.0	$ 0.0	$ (4.0)
Balance at end of period (in shares) | shares				2,178,000,000	2,125,000,000	2,025,000,000
Balance at end of period, amount				$ 71,738.0	$ 69,180.0	$ 64,760.0
Common Shares | At-The-Market Offering
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Sale of stock, number of shares issued in transaction (shares) | shares			51,298,629
Sale of stock, price per share (in Canadian dollars per share and US dollars per share) | (per share)			$ 48.72				$ 35.77