PENSION AND OTHER POSTRETIREMENT BENEFITS - Fair Value Hierarchy of the Plan Assets Measured at Fair Value Value on a Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 202	$ 294
Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	76	86
Collective trusts
Defined Benefit Plan Disclosure [Line Items]
Plan assets	37	102
Equity index trusts
Defined Benefit Plan Disclosure [Line Items]
Plan assets	86	94
Money markets
Defined Benefit Plan Disclosure [Line Items]
Plan assets	2	10
Bond index funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1	2
Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	162	181
Level 1 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	76	86
Level 1 | Collective trusts
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 1 | Equity index trusts
Defined Benefit Plan Disclosure [Line Items]
Plan assets	86	94
Level 1 | Money markets
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	1
Level 1 | Bond index funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	4	12
Level 2 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 2 | Collective trusts
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1	1
Level 2 | Equity index trusts
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 2 | Money markets
Defined Benefit Plan Disclosure [Line Items]
Plan assets	2	9
Level 2 | Bond index funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1	2
Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	36	101
Level 3 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 3 | Collective trusts
Defined Benefit Plan Disclosure [Line Items]
Plan assets	36	101
Level 3 | Equity index trusts
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 3 | Money markets
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 3 | Bond index funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 0	$ 0