LONG-TERM DEBT - Long-Term Debt by Types and Interest Rates (Includes Current Portion) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Other	$ 1	$ 1
Long-term debt, before unamortized discounts	5,933	6,008
Less unamortized discounts	(5)	(5)
Less unamortized debt expense	(9)	(11)
Total	5,919	5,992
Portion due within one year	$ 500	62
Debt, maturity date	Mar. 31, 2022
7.00% debentures due 2018
Debt Instrument [Line Items]
Senior Notes	$ 0	62
Debt, interest rate	7.00%
Debt, maturity date	Dec. 31, 2018
7.375% notes due 2019
Debt Instrument [Line Items]
Senior Notes	$ 500	500
Debt, interest rate	7.375%
Debt, maturity date	Dec. 31, 2019
9.00% debentures due 2021
Debt Instrument [Line Items]
Senior Notes	$ 150	150
Debt, interest rate	9.00%
Debt, maturity date	Dec. 31, 2021
4.70% debentures due 2021
Debt Instrument [Line Items]
Senior Notes	$ 588	597
Debt, interest rate	4.70%
Debt, maturity date	Dec. 31, 2021
7.125% debentures due 2023
Debt Instrument [Line Items]
Senior Notes	$ 191	191
Debt, interest rate	7.125%
Debt, maturity date	Dec. 31, 2023
5.207% debentures due 2023
Debt Instrument [Line Items]
Senior Notes	$ 881	885
Debt, interest rate	5.207%
Debt, maturity date	Dec. 31, 2023
4.625% notes due 2023
Debt Instrument [Line Items]
Senior Notes	$ 500	500
Debt, interest rate	4.625%
Debt, maturity date	Dec. 31, 2023
3.25% debentures due 2023
Debt Instrument [Line Items]
Senior Notes	$ 324	324
Debt, interest rate	3.25%
Debt, maturity date	Dec. 31, 2023
8.50% debentures due 2025
Debt Instrument [Line Items]
Senior Notes	$ 300	300
Debt, interest rate	8.50%
Debt, maturity date	Dec. 31, 2025
7.95% debentures due 2025
Debt Instrument [Line Items]
Senior Notes	$ 136	136
Debt, interest rate	7.95%
Debt, maturity date	Dec. 31, 2025
7.70% debentures due 2026
Debt Instrument [Line Items]
Senior Notes	$ 150	150
Debt, interest rate	7.70%
Debt, maturity date	Dec. 31, 2026
7.35% debentures due 2026
Debt Instrument [Line Items]
Senior Notes	$ 62	62
Debt, interest rate	7.35%
Debt, maturity date	Dec. 31, 2026
7.85% debentures due 2026
Debt Instrument [Line Items]
Senior Notes	$ 100	100
Debt, interest rate	7.85%
Debt, maturity date	Dec. 31, 2026
Variable rate term loan credit facility matures 2026
Debt Instrument [Line Items]
Term loan credit facility	$ 225	225
Debt, interest rate	4.122%
Debt, maturity date	Dec. 31, 2026
6.95% debentures due 2027
Debt Instrument [Line Items]
Senior Notes	$ 300	300
Debt, interest rate	6.95%
Debt, maturity date	Dec. 31, 2027
7.375% debentures due 2032
Debt Instrument [Line Items]
Senior Notes	$ 1,250	1,250
Debt, interest rate	7.375%
Debt, maturity date	Dec. 31, 2032
6.875% debentures due 2033
Debt Instrument [Line Items]
Senior Notes	$ 275	$ 275
Debt, interest rate	6.875%
Debt, maturity date	Dec. 31, 2033

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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Amount, after accumulated amortization, of debt discount (premium).

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Date the credit facility terminates, in CCYY-MM-DD format.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The carrying value as of the balance sheet date of the noncurrent portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Amount of long-term debt classified as other.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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