RETIREMENT BENEFITS - Level 3 (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of fiscal year	$ 1,162
Sale of securities	(3)
Transfers into Level 3	0
Plan assets at fair value at end of fiscal year	1,173	$ 1,162
Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Plan assets at fair value at beginning of fiscal year	4	0
Purchase of securities	16	4
Change in the fair value	(2)	0
Transfers out of Level 3	(1)
Plan assets at fair value at end of fiscal year	$ 14	$ 4