Long-Term Debt (Extinguishment of Debt) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Extinguishment of Debt [Line Items]
Premiums and fees									$ 226	$ 44	$ 1,054
Write-off of unamortized debt discounts and debt issuance costs									2	0	30
Loss on early extinguishment of debt	$ 0	$ 0	$ 0	$ 228	$ 44	$ 0	$ 0	$ 0	228	$ 44	1,084
Senior Notes [Member]
Extinguishment of Debt [Line Items]
Notes purchased									793		2,100
9.95% Note [Member] | Senior Notes [Member]
Extinguishment of Debt [Line Items]
Notes purchased									$ 0		$ 818
Stated interest rate	9.95%								9.95%		9.95%
10.20% Note [Member] | Senior Notes [Member]
Extinguishment of Debt [Line Items]
Notes purchased									$ 0		$ 782
Stated interest rate	10.20%								10.20%		10.20%
9.70% Note[Member] | Senior Notes [Member]
Extinguishment of Debt [Line Items]
Notes purchased									$ 793		$ 293
Stated interest rate	9.70%								9.70%		9.70%
9.25% Note [Member] | Senior Notes [Member]
Extinguishment of Debt [Line Items]
Notes purchased									$ 0		$ 207
Stated interest rate	9.25%								9.25%		9.25%