Schedule II - Condensed Financial Information, Short-term and Long-term Debt (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Debt Instrument [Line Items]
Total short-term debt	$ 999		$ 147
Long-term debt, carrying value	5,062		5,005
Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Commercial paper	100		100
Total short-term debt	999		147
Long-term debt, carrying value	5,062		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	257	[1]	254	[1]
$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	306	[1]	303	[1]
$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	307	[1]	303	[1]
$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.