EMPLOYEE BENEFIT PLANS (Additional Information) (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) plan	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Number of defined benefit pension plans | plan	3
Number of qualified defined benefit pension plans | plan	2
Increase in pension benefit obligation	$ 85,000,000
Increase in pension plan assets	$ 70,000,000
Percentage of service cost that was capitalized (in percentage)	21.00%	19.00%
Investment return model best-estimate range (in years)	20 years
Matching 401(k) contributions made	$ 6,000,000	$ 7,000,000	$ 6,000,000
Level 3
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value measurements of plan assets	28,000,000	28,000,000	27,000,000
Other Postretirement Benefits
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Employer Contribution to VEBA Trust	1,000,000	3,000,000	3,000,000
Fair value measurements of plan assets	21,000,000	17,000,000	17,000,000
Other Postretirement Benefits | Level 1 and Level 2
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value measurements of plan assets	21,000,000	17,000,000
Other Postretirement Benefits | Level 3
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value measurements of plan assets	0
Pension Benefits
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Accumulated benefit obligation	476,000,000	402,000,000
Fair value measurements of plan assets	446,000,000	376,000,000	$ 403,000,000
Pension Benefits | Level 3
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value measurements of plan assets	28,000,000	28,000,000
Transfers	$ 0
Minimum
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Percentile of investment return model range used (in percentage)	25.00%
Maximum
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Percentile of investment return model range used (in percentage)	75.00%
Fixed Income Securities | Other Postretirement Benefits | Level 1 and Level 2
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value measurements of plan assets	$ 7,000,000	7,000,000
Equities | Other Postretirement Benefits | Level 1 and Level 2
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Fair value measurements of plan assets	$ 14,000,000	$ 10,000,000