Schedule II - Condensed Financial Information, Short-term and Long-term Debt (Details) - USD ($) $ in Millions		Jun. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Total short-term debt		$ 150	$ 147
Long-term debt, carrying value		5,046	5,005
Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Commercial paper		100	100
Total short-term debt		150	147
Long-term debt, carrying value		$ 5,046	$ 5,005
$600 million, 2.75% Notes due 2016 [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, stated interest rate		2.75%	2.75%
Long-term debt, carrying value		$ 0	$ 600
$250 million, 5.375% Notes due 2017 [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, stated interest rate		5.375%	5.375%
Long-term debt, carrying value		$ 250	$ 250
$131 million, 6.35% Notes due 2018 [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, stated interest rate		6.35%	6.35%
Long-term debt, carrying value		$ 131	$ 131
$251 million, 8.5% Notes due 2019 [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, stated interest rate		8.50%	8.50%
Long-term debt, carrying value		$ 0	$ 251
$250 million, 4.375% Notes due 2020 [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, stated interest rate		4.375%	4.375%
Long-term debt, carrying value	[1]	$ 254	$ 254
$300 million, 5.125% Notes due 2020 [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, stated interest rate		5.125%	5.125%
Long-term debt, carrying value	[1]	$ 303	$ 303
$300 million, 4.5% Notes due 2021 [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, stated interest rate		4.50%	4.50%
Long-term debt, carrying value	[1]	$ 303	$ 303
$750 million, 4% Notes due 2022 [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, stated interest rate		4.00%	4.00%
Long-term debt, carrying value		$ 745	$ 745
$100 million, 7.65% Notes due 2023 [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
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, stated interest rate		8.30%	8.30%
Long-term debt, carrying value		$ 17	$ 17
$300 million, 7.875% Debentures due 2027 [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, stated interest rate		7.875%	7.875%
Long-term debt, carrying value		$ 300	$ 300
$83 million, 8.3% Step Down Notes due 2033 [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, stated interest rate		8.30%	8.30%
Long-term debt, carrying value		$ 83	$ 83
$500 million, 6.15% Notes due 2036 [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, stated interest rate		6.15%	6.15%
Long-term debt, carrying value		$ 500	$ 500
$300 million, 5.875% Notes due 2041 [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, stated interest rate		5.875%	5.875%
Long-term debt, carrying value		$ 298	$ 298
$750 million, 5.375% Notes due 2042 [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt, stated interest rate		5.375%	5.375%
Long-term debt, carrying value		$ 750	$ 750

[1] The Company has entered into interest rate swap contracts hedging a portion of these fixed-rate debt instruments. See Note 9 for further information about the Company’s interest rate risk management and these derivative instruments.