Debt - Extinguishment (Details) - Uncollateralized Debt [Member] - USD ($)		3 Months Ended		6 Months Ended
	Apr. 13, 2015	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Extinguishment of Debt [Line Items]
Extinguishment of Debt, Gain (Loss), Net of Tax		$ (65,000,000)	$ 0	$ (65,000,000)	$ 0
Notes due 2016 2.75% Interest [Member]
Extinguishment of Debt [Line Items]
Extinguishment of Debt, Amount	$ 626,000,000
Extinguishment of Debt, Gain (Loss), Net of Tax	$ (14,000,000)
Applicable Treasury Rate Duration For Debt Redemptions	10 years
Basis Points Added To Treasury Rate	0.30%
Notes due 2019 8.5% Interest [Member]
Extinguishment of Debt [Line Items]
Extinguishment of Debt, Amount	$ 329,000,000
Extinguishment of Debt, Gain (Loss), Net of Tax	$ (51,000,000)
Applicable Treasury Rate Duration For Debt Redemptions	10 years
Basis Points Added To Treasury Rate	0.50%