PROPERTY AND EQUIPMENT - Carrying Value of Property and Equipment and Estimated Service Lives (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property and Equipment [Line Items]
Property and equipment, at cost	$ 5,233	$ 4,956
Accumulated depreciation and amortization	(3,376)	(3,338)
Property and equipment, net	1,857	1,618
Land
Property and Equipment [Line Items]
Property and equipment, at cost	87	88
Buildings and improvements
Property and Equipment [Line Items]
Property and equipment, at cost	942	867
Machinery and equipment
Property and Equipment [Line Items]
Property and equipment, at cost	3,240	3,037
Roads
Property and Equipment [Line Items]
Property and equipment, at cost	785	782
Other
Property and Equipment [Line Items]
Property and equipment, at cost	$ 179	$ 182
Minimum | Buildings and improvements
Property and Equipment [Line Items]
Estimated service lives	15 years
Minimum | Machinery and equipment
Property and Equipment [Line Items]
Estimated service lives	5 years
Minimum | Roads
Property and Equipment [Line Items]
Estimated service lives	10 years
Minimum | Other
Property and Equipment [Line Items]
Estimated service lives	3 years
Maximum | Buildings and improvements
Property and Equipment [Line Items]
Estimated service lives	40 years
Maximum | Machinery and equipment
Property and Equipment [Line Items]
Estimated service lives	25 years
Maximum | Roads
Property and Equipment [Line Items]
Estimated service lives	35 years
Maximum | Other
Property and Equipment [Line Items]
Estimated service lives	10 years