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.