RETIREMENT BENEFITS - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Plan asset amortization period	5 years
Pension plans
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 60,000,000	$ 58,000,000
Expected future employer contributions, next fiscal year	0
Actuarial losses	$ (393,000,000)	$ 1,679,000,000
Change in discount rate	0.28%	(0.60%)
Pension plans | Qualified pension plan
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 0
Other postretirement benefit plans
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	43,000,000	$ 72,000,000
Expected future employer contributions, next fiscal year	0
Actuarial losses	$ (54,000,000)	$ 7,000,000