Schedule II - Condensed Financial Information, Short-term and Long-term Debt (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total short-term debt	$ 141	$ 276
Long-term debt, carrying value	4,622	4,756
Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	131	250
Other, including capital leases	10	26
Total short-term debt	141	276
Long-term debt, carrying value	4,622	4,756
$131 million, 6.35% Notes due 2018 [Member] \| Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, face value	$ 131	$ 131
Long-term debt, stated interest rate	6.35%	6.35%
Long-term debt, carrying value	$ 0	$ 131
$250 million, 4.375% Notes due 2020 [Member] \| Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, face value	$ 250	$ 250
Long-term debt, stated interest rate	4.375%	4.375%
Long-term debt, carrying value	$ 252	$ 252
$300 million, 5.125% Notes due 2020 [Member] \| Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, face value	$ 300	$ 300
Long-term debt, stated interest rate	5.125%	5.125%
Long-term debt, carrying value	$ 302	$ 301
$300 million, 4.5% Notes due 2021 [Member] \| Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, face value	$ 300	$ 300
Long-term debt, stated interest rate	4.50%	4.50%
Long-term debt, carrying value	$ 302	$ 302
$750 million, 4% Notes due 2022 [Member] \| Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, face value	$ 750	$ 750
Long-term debt, stated interest rate	4.00%	4.00%
Long-term debt, carrying value	$ 744	$ 744
$100 million, 7.65% Notes due 2023 [Member] \| Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, face value	$ 100	$ 100
Long-term debt, stated interest rate	7.65%	7.65%
Long-term debt, carrying value	$ 100	$ 100
$17 million, 8.3% Notes due 2023 [Member] \| Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, face value	$ 17	$ 17
Long-term debt, stated interest rate	8.30%	8.30%
Long-term debt, carrying value	$ 17	$ 17
$900 million, 3.25% Notes Due 2025 [Member] \| Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, face value	$ 900	$ 900
Long-term debt, stated interest rate	3.25%	3.25%
Long-term debt, carrying value	$ 894	$ 893
$300 million, 7.875% Debentures due 2027 [Member] \| Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, face value	$ 300	$ 300
Long-term debt, stated interest rate	7.875%	7.875%
Long-term debt, carrying value	$ 299	$ 299
$83 million, 8.3% Step Down Notes due 2033 [Member] \| Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, face value	$ 83	$ 83
Long-term debt, stated interest rate	8.30%	8.30%
Long-term debt, carrying value	$ 82	$ 82
$500 million, 6.15% Notes due 2036 [Member] \| Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, face value	$ 500	$ 500
Long-term debt, stated interest rate	6.15%	6.15%
Long-term debt, carrying value	$ 498	$ 498
$300 million, 5.875% Notes due 2041 [Member] \| Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, face value	$ 300	$ 300
Long-term debt, stated interest rate	5.875%	5.875%
Long-term debt, carrying value	$ 296	$ 296
$750 million, 5.375% Notes due 2042 [Member] \| Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, face value	$ 750	$ 750
Long-term debt, stated interest rate	5.375%	5.375%
Long-term debt, carrying value	$ 743	$ 743

Amount of capital lease obligation due within one year or the normal operating cycle, if longer.

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