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

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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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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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a rate subject to change from time to time.

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LONG-TERM DEBT - SCHEDULE (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Nov. 30, 2016	Apr. 30, 2016	Jun. 30, 2015
LONG-TERM DEBT
Long-term debt, gross	$ 9,907	$ 9,907
Unamortized discount, net	(32)	(36)
Debt issuance costs	(47)	(52)
Current maturities	(500)
Total long-term debt	9,328	9,819
1.50% senior notes due 2018
LONG-TERM DEBT
Long-term debt, gross	$ 500	$ 500
Debt instrument interest rate stated percentage	1.50%	1.50%
9.25% senior debentures due 2019
LONG-TERM DEBT
Long-term debt, gross	$ 116	$ 116
Debt instrument interest rate stated percentage	9.25%	9.25%
4.10% senior notes due 2021
LONG-TERM DEBT
Long-term debt, gross	$ 1,249	$ 1,249
Debt instrument interest rate stated percentage	4.10%	4.10%
3.125% senior notes due 2022
LONG-TERM DEBT
Long-term debt, gross	$ 813	$ 813
Debt instrument interest rate stated percentage	3.125%	3.125%
2.60% senior notes due 2022
LONG-TERM DEBT
Long-term debt, gross	$ 400	$ 400
Debt instrument interest rate stated percentage	2.60%	2.60%		2.60%
2.70% senior notes due 2023
LONG-TERM DEBT
Long-term debt, gross	$ 1,191	$ 1,191
Debt instrument interest rate stated percentage	2.70%	2.70%
8.75% medium-term notes due 2023
LONG-TERM DEBT
Long-term debt, gross	$ 22	$ 22
Debt instrument interest rate stated percentage	8.75%	8.75%
3.50% senior notes due 2025
LONG-TERM DEBT
Long-term debt, gross	$ 750	$ 750
Debt instrument interest rate stated percentage	3.50%	3.50%			3.50%
3.40% senior notes due 2026
LONG-TERM DEBT
Long-term debt, gross	$ 1,150	$ 1,150
Debt instrument interest rate stated percentage	3.40%	3.40%		3.40%
3.00% senior notes due 2027
LONG-TERM DEBT
Long-term debt, gross	$ 750	$ 750
Debt instrument interest rate stated percentage	3.00%	3.00%	3.00%
7.20% senior debentures due 2028
LONG-TERM DEBT
Long-term debt, gross	$ 82	$ 82
Debt instrument interest rate stated percentage	7.20%	7.20%
8.45% senior notes due 2029
LONG-TERM DEBT
Long-term debt, gross	$ 116	$ 116
Debt instrument interest rate stated percentage	8.45%	8.45%
4.625% senior notes due 2045
LONG-TERM DEBT
Long-term debt, gross	$ 750	$ 750
Debt instrument interest rate stated percentage	4.625%	4.625%			4.625%
4.40% senior notes due 2046
LONG-TERM DEBT
Long-term debt, gross	$ 1,200	$ 1,200
Debt instrument interest rate stated percentage	4.40%	4.40%		4.40%
4.10% senior notes due 2047
LONG-TERM DEBT
Long-term debt, gross	$ 750	$ 750
Debt instrument interest rate stated percentage	4.10%	4.10%	4.10%
Variable rate bonds due 2030 (0.9% and 0.15% as of December 31, 2016 and 2015, respectively )
LONG-TERM DEBT
Variable interest rate (as a percent)	1.80%	0.90%
Long-term debt, gross	$ 68	$ 68