Long-Term Debt (Long-Term Debt) (Details) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Long-term debt, beginning balance		$ 9,781
Payments and Retirements		(250)
New Borrowings		3
Long-term debt, ending balance		9,781	$ 9,534	$ 9,781
Less: Debt (Discount)/Premium			3	3
Less: Current Portion			(97)	(298)
Principal Outstanding			$ 9,440	9,486
Weighted average interest rate	[1]		7.68%
Senior Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term debt, beginning balance		9,750
Payments and Retirements		$ (248)
New Borrowings
Long-term debt, ending balance		$ 9,750	$ 9,502	9,750
Weighted average interest rate	[1]		7.69%
Other Secured Debt [Member]
Debt Instrument [Line Items]
Long-term debt, beginning balance		23
Payments and Retirements		(2)
New Borrowings		3
Long-term debt, ending balance		23	$ 24	23
Weighted average interest rate	[1]		3.50%
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 June 30, 2015 represent a weighted average of multiple issuances.