DEBT AND FINANCING COSTS - Schedule of Debt (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Finance lease obligations	$ 63
Capital lease obligations		$ 40
Unamortized discount	(43)	(44)
Debt issuance costs	(55)	(51)
Total debt	8,332	8,244
Current maturities	(175)	(151)
Long-term debt	8,157	8,093
Notes And Debentures \| Unsecured Debt
Debt Instrument [Line Items]
Long-term debt, gross	$ 8,367	$ 8,299

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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