PENSION AND OTHER POST-EMPLOYMENT BENEFIT PLANS - Net Pension Plan Assets, by Fair Value Hierarchy (Details) - Pension - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Cash and short-term investments | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	$ 69	$ 82
Cash and short-term investments | Non Registered Plans | Canada
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	4	5
Public equity investments | Qualified and Registered Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	249	17
Fixed Income Investments, Corporate | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	562	907
Fixed Income Investments, Government | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	366	337
Fixed Income Investments, Repurchase Agreements | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	(25)
Hedge funds and related investments | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	16	21
Private equity and related investments | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	2	26
Derivative instruments, net | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	(1)	1
Pension trust investments measured at fair value | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	1,263	1,366
Public equity investments | Non Registered Plans | Canada
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	4	4
Canadian nonregistered plan assets measured at fair value | Non Registered Plans | Canada
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	8	9
Pension plans defined benefit excluding hedge fund and private equity investments and accrued liabilities
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	1,271	1,375
Fair Value, Inputs, Level 1 | Cash and short-term investments | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	69	82
Fair Value, Inputs, Level 1 | Cash and short-term investments | Non Registered Plans | Canada
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	4	5
Fair Value, Inputs, Level 1 | Public equity investments | Qualified and Registered Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	249	17
Fair Value, Inputs, Level 1 | Fixed Income Investments, Corporate | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 1 | Fixed Income Investments, Government | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 1 | Fixed Income Investments, Repurchase Agreements | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 1 | Hedge funds and related investments | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 1 | Private equity and related investments | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 1 | Derivative instruments, net | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 1 | Pension trust investments measured at fair value | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	318	99
Fair Value, Inputs, Level 1 | Public equity investments | Non Registered Plans | Canada
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	4	4
Fair Value, Inputs, Level 1 | Canadian nonregistered plan assets measured at fair value | Non Registered Plans | Canada
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	8	9
Fair Value, Inputs, Level 2 | Cash and short-term investments | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 2 | Cash and short-term investments | Non Registered Plans | Canada
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 2 | Public equity investments | Qualified and Registered Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 2 | Fixed Income Investments, Corporate | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	562	907
Fair Value, Inputs, Level 2 | Fixed Income Investments, Government | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	366	337
Fair Value, Inputs, Level 2 | Fixed Income Investments, Repurchase Agreements | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	(25)
Fair Value, Inputs, Level 2 | Hedge funds and related investments | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 2 | Private equity and related investments | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 2 | Derivative instruments, net | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	(1)	1
Fair Value, Inputs, Level 2 | Pension trust investments measured at fair value | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	927	1,220
Fair Value, Inputs, Level 2 | Public equity investments | Non Registered Plans | Canada
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 2 | Canadian nonregistered plan assets measured at fair value | Non Registered Plans | Canada
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 3 | Cash and short-term investments | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 3 | Cash and short-term investments | Non Registered Plans | Canada
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 3 | Public equity investments | Qualified and Registered Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 3 | Fixed Income Investments, Corporate | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 3 | Fixed Income Investments, Government | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 3 | Fixed Income Investments, Repurchase Agreements | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 3 | Hedge funds and related investments | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	16	21
Fair Value, Inputs, Level 3 | Private equity and related investments | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	2	26
Fair Value, Inputs, Level 3 | Derivative instruments, net | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 3 | Pension trust investments measured at fair value | Qualified and Registered Plans | U.S.
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	18	47
Fair Value, Inputs, Level 3 | Public equity investments | Non Registered Plans | Canada
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	0	0
Fair Value, Inputs, Level 3 | Canadian nonregistered plan assets measured at fair value | Non Registered Plans | Canada
Defined Benefit Plan Disclosure [Line Items]
Fair value of net plan assets	$ 0	$ 0