RETIREMENT BENEFITS Retirement Benefits - Obligations and Funded Status (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Service Cost		$ 1	$ 1	$ 1
Interest cost		3	3	2
Fair value of plan assets at beginning of period		169
Fair value of plan assets at end of period		191	169
Other Postretirement Benefits Plan [Member]
Benefit obligation at beginning of period		91	78
Defined Benefit Plan, Service Cost		1	1
Interest cost		3	3
Actuarial loss		7	12
Benefit obligation at end of period		98	91	78
Fair value of plan assets at beginning of period		169	141
Return on plan assets and other		18	23
Employer contributions		8	8
Defined Benefit Plan, Benefit Obligation, Benefits Paid		4	3
Fair value of plan assets at end of period		191	169	$ 141
Amount overfunded at end of period (1)	[1]	93	78
Net actuarial gain		(8)	(5)
Prior service cost		19	37
Amounts recognized in accumulated other comprehensive loss (pre-tax basis) consist of:		$ 11	$ 32

[1] Recorded as a non-current asset in the consolidated balance sheets.