RETIREMENT AND OTHER BENEFIT PROGRAMS - Summary of Net-of-Tax Amounts Recorded in OCI Relating to Pension and OPEB Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of the net-of-tax amounts recorded in OCI relating to pension and OPEB plans
Gain (loss) arising during the year, net of tax expense (benefit) of $(64) in 2019, $(4) in 2018 and $25 in 2017	$ (184)	$ (22)	$ 32
Amortization of loss to earnings, net of tax benefit of $6 in 2019, $14 in 2018 and $35 in 2017	25	55	102
Settlement charge, net of tax benefit of $188 in 2019	567	0	0
Pension and other employee benefits gain	408	33	134
Gain (loss) arising during the year, tax expense (benefit)	(64)	(4)	25
Amortization of loss to earnings, tax benefit	6	$ 14	$ 35
Settlement, tax benefit	$ (188)