Long-Term Debt (Senior Unsecured Debt) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended					3 Months Ended
	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2014		Jun. 30, 2013	May 17, 2012	Apr. 10, 2013	Aug. 15, 2012
Debt Instrument [Line Items]
Principal Outstanding	8,129,546			9,780,736
Senior Note Due 5/1/2014 [Member]
Debt Instrument [Line Items]
Interest Rate							8.25%
Debt instrument, maturity date	May 01, 2014
Senior Note Due 3/15/2015 [Member]
Debt Instrument [Line Items]
Interest Rate								6.625%
Debt instrument, maturity date	Mar. 15, 2015
Senior Note Due 4/15/2015 [Member]
Debt Instrument [Line Items]
Interest Rate								7.875%
Debt instrument, maturity date	Apr. 15, 2015		Apr. 01, 2015
Senior Note Due 10/14/2016 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Oct. 14, 2016	[1]
Senior Note Due 4/15/2017 [Member]
Debt Instrument [Line Items]
Interest Rate	8.25%
Debt instrument, maturity date	Apr. 15, 2017
Senior Note Due 10/1/2018 [Member]
Debt Instrument [Line Items]
Interest Rate						8.125%
Debt instrument, maturity date						Oct. 01, 2018
Senior Note Due 10/24/2019 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Oct. 24, 2019	[2]
Senior Note Due 4/15/2020 [Member]
Debt Instrument [Line Items]
Interest Rate						8.50%
Debt instrument, maturity date						Apr. 15, 2020
Senior Note Due 7/1/2021 [Member]
Debt Instrument [Line Items]
Interest Rate							9.25%
Debt instrument, maturity date	Jul. 01, 2021
Senior Note Due 1/15/2023 [Member]
Debt Instrument [Line Items]
Interest Rate									7.125%
Debt instrument, maturity date	Jan. 15, 2023
Senior Unsecured Debt [Member]
Debt Instrument [Line Items]
Principal Outstanding	8,107,066			9,749,566
Weighted average interest rate	7.78%	[3]		7.45%	[3]
Senior Unsecured Debt [Member] | Senior Note Due 10/14/2016 [Member]
Debt Instrument [Line Items]
Principal Outstanding	460,000			402,500
Interest Rate	3.045%			3.045%
Senior Unsecured Debt [Member] | Senior Note Due 10/24/2019 [Member]
Debt Instrument [Line Items]
Principal Outstanding				350,000
Interest Rate				3.545%
Senior Notes and Debentures [Member] | Senior Note Due 5/1/2014 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				May 01, 2014
Senior Notes and Debentures [Member] | Senior Note Due 3/15/2015 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Mar. 15, 2015
Senior Notes and Debentures [Member] | Senior Note Due 4/15/2015 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Apr. 15, 2015
Senior Notes and Debentures [Member] | Senior Note Due 4/15/2017 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Apr. 15, 2017
Senior Notes and Debentures [Member] | Senior Note Due 10/1/2018 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Oct. 01, 2018
Senior Notes and Debentures [Member] | Senior Note Due 3/15/2019 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Mar. 15, 2019
Senior Notes and Debentures [Member] | Senior Note Due 4/15/2020 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Apr. 15, 2020
Senior Notes and Debentures [Member] | Senior Note Due 7/1/2021 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Jul. 01, 2021
Senior Notes and Debentures [Member] | Senior Note Due 9/15/2021 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Sep. 15, 2021
Senior Notes and Debentures [Member] | Senior Note Due 4/15/2022 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Apr. 15, 2022
Senior Notes and Debentures [Member] | Senior Note Due 1/15/2023 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Jan. 15, 2023
Senior Notes and Debentures [Member] | Senior Note Due 4/15/2024 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Apr. 15, 2024
Senior Notes and Debentures [Member] | Senior Note Due 1/15/2025 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Jan. 15, 2025
Senior Notes and Debentures [Member] | Debenture Due 11/1/2025 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Nov. 01, 2025
Senior Notes and Debentures [Member] | Debenture Due 8/15/2026 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Aug. 15, 2026
Senior Notes and Debentures [Member] | Senior Note Due 1/15/2027 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Jan. 15, 2027
Senior Notes and Debentures [Member] | Senior Note Due 8/15/2031 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Aug. 15, 2031
Senior Notes and Debentures [Member] | Debenture Due 10/1/2034 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Oct. 01, 2034
Senior Notes and Debentures [Member] | Debenture Due 7/1/2035 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Jul. 01, 2035
Senior Notes and Debentures [Member] | Debenture Due 10/1/2046 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Oct. 01, 2046
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member]
Debt Instrument [Line Items]
Principal Outstanding	7,857,066			9,499,566
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Senior Note Due 5/1/2014 [Member]
Debt Instrument [Line Items]
Principal Outstanding	200,000
Interest Rate	8.25%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Senior Note Due 3/15/2015 [Member]
Debt Instrument [Line Items]
Principal Outstanding	105,026			105,026
Interest Rate	6.625%			6.625%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Senior Note Due 4/15/2015 [Member]
Debt Instrument [Line Items]
Principal Outstanding	96,872			96,872
Interest Rate	7.875%			7.875%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Senior Note Due 10/14/2016 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Oct. 14, 2016
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Senior Note Due 4/15/2017 [Member]
Debt Instrument [Line Items]
Principal Outstanding	606,874			606,874
Interest Rate	8.25%			8.25%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Senior Note Due 10/1/2018 [Member]
Debt Instrument [Line Items]
Principal Outstanding	582,739			582,739
Interest Rate	8.125%			8.125%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Senior Note Due 3/15/2019 [Member]
Debt Instrument [Line Items]
Principal Outstanding	434,000			434,000
Interest Rate	7.125%			7.125%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Senior Note Due 10/24/2019 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Oct. 24, 2019
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Senior Note Due 4/15/2020 [Member]
Debt Instrument [Line Items]
Principal Outstanding	1,021,505			1,021,505
Interest Rate	8.50%			8.50%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Senior Note Due 7/1/2021 [Member]
Debt Instrument [Line Items]
Principal Outstanding	500,000			500,000
Interest Rate	9.25%			9.25%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Senior Note Due 9/15/2021 [Member]
Debt Instrument [Line Items]
Principal Outstanding				775,000
Interest Rate				6.25%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Senior Note Due 4/15/2022 [Member]
Debt Instrument [Line Items]
Principal Outstanding	500,000			500,000
Interest Rate	8.75%			8.75%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Senior Note Due 1/15/2023 [Member]
Debt Instrument [Line Items]
Principal Outstanding	850,000			850,000
Interest Rate	7.125%			7.125%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Senior Note Due 4/15/2024 [Member]
Debt Instrument [Line Items]
Principal Outstanding	750,000			750,000
Interest Rate	7.625%			7.625%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Senior Note Due 1/15/2025 [Member]
Debt Instrument [Line Items]
Principal Outstanding				775,000
Interest Rate				6.875%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Debenture Due 11/1/2025 [Member]
Debt Instrument [Line Items]
Principal Outstanding	138,000			138,000
Interest Rate	7.00%			7.00%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Debenture Due 8/15/2026 [Member]
Debt Instrument [Line Items]
Principal Outstanding	1,739			1,739
Interest Rate	6.80%			6.80%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Senior Note Due 1/15/2027 [Member]
Debt Instrument [Line Items]
Principal Outstanding	345,858			345,858
Interest Rate	7.875%			7.875%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Senior Note Due 8/15/2031 [Member]
Debt Instrument [Line Items]
Principal Outstanding	945,325			945,325
Interest Rate	9.00%			9.00%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Debenture Due 10/1/2034 [Member]
Debt Instrument [Line Items]
Principal Outstanding	628			628
Interest Rate	7.68%			7.68%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Debenture Due 7/1/2035 [Member]
Debt Instrument [Line Items]
Principal Outstanding	125,000			125,000
Interest Rate	7.45%			7.45%
Senior Notes and Debentures [Member] | Senior Unsecured Debt [Member] | Debenture Due 10/1/2046 [Member]
Debt Instrument [Line Items]
Principal Outstanding	193,500			193,500
Interest Rate	7.05%			7.05%
Subsidiary Debentures [Member] | Subsidiary Senior Note Due 2/15/2028 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Feb. 15, 2028
Subsidiary Debentures [Member] | Subsidiary Senior Note Due 10/15/2029 [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date				Oct. 15, 2029
Subsidiary Debentures [Member] | Senior Unsecured Debt [Member] | Subsidiary Senior Note Due 2/15/2028 [Member]
Debt Instrument [Line Items]
Principal Outstanding	200,000			200,000
Interest Rate	6.73%			6.73%
Subsidiary Debentures [Member] | Senior Unsecured Debt [Member] | Subsidiary Senior Note Due 10/15/2029 [Member]
Debt Instrument [Line Items]
Principal Outstanding	50,000			50,000
Interest Rate	8.40%			8.40%

[1] * Represents borrowings under the 2011 CoBank Credit Agreement, as defined below.

[2] ** Represents borrowings under the 2014 CoBank Credit Agreement, as defined below.

[3] *** Interest rate represents a weighted average of the stated interest rates of multiple issuances.