Long-Term Debt (Long-Term Debt) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Long-term debt, beginning balance		$ 16,086
Payments and Retirements		(24)
Long-term debt, ending balance		16,086	$ 16,062	$ 16,086
Less: Debt Issuance Cost			(198)	(196)
Less: Debt Premium			2	2
Less: Current Portion			(370)	(384)
Principal Outstanding			$ 15,496	15,508
Weighted average interest rate	[1]		9.04%
Senior Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term debt, beginning balance		16,055
Payments and Retirements		$ (23)
New Borrowings
Long-term debt, ending balance		$ 16,055	$ 16,032	16,055
Weighted average interest rate	[1]		9.04%
Other Secured Debt [Member]
Debt Instrument [Line Items]
Long-term debt, beginning balance		23
Payments and Retirements		$ (1)
New Borrowings
Long-term debt, ending balance		$ 23	$ 22	23
Weighted average interest rate	[1]		3.94%
Rural Utilities Service Loan Contracts [Member]
Debt Instrument [Line Items]
Long-term debt, beginning balance		$ 8
Payments and Retirements
New Borrowings
Long-term debt, ending balance		$ 8	$ 8	$ 8
Weighted average interest rate	[1]		6.15%

[1] Interest rate includes amortization of debt issuance costs and debt premiums or discounts. The interest rates at March 31, 2016 represent a weighted average of multiple issuances.