Long-Term Debt (Long-Term Debt) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013		Dec. 31, 2012
Debt Instrument [Line Items]
Long-term debt, beginning balance	$ 8,942,568
Payments and Retirements	(1,548,548)
New Borrowings	750,000
Long-term debt, ending balance	8,144,020
Less: Debt (Discount)/Premium	1,186		(71)
Less: Current Portion	(257,910)		(560,550)
Principal Outstanding	7,887,296		8,381,947
Weighted average interest rate	7.96%	[1]
Senior Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term debt, beginning balance	8,919,696
Payments and Retirements	(1,548,255)
New Borrowings	750,000
Long-term debt, ending balance	8,121,441
Weighted average interest rate	7.96%	[1]
Industrial Development Revenue Bonds [Member]
Debt Instrument [Line Items]
Long-term debt, beginning balance	13,550
Payments and Retirements
New Borrowings
Long-term debt, ending balance	13,550
Weighted average interest rate	6.33%	[1]
Rural Utilities Service Loan Contracts [Member]
Debt Instrument [Line Items]
Long-term debt, beginning balance	9,322
Payments and Retirements	(293)
Long-term debt, ending balance	$ 9,029
Weighted average interest rate	6.15%	[1]

[1] Interest rate includes amortization of debt issuance costs and debt premiums or discounts. The interest rates at September 30, 2013 represent a weighted average of multiple issuances.