Long-Term Debt (Details) (USD $)	3 Months Ended			9 Months Ended										9 Months Ended							9 Months Ended		9 Months Ended	3 Months Ended	6 Months Ended	9 Months Ended																																																						9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011	Sep. 30, 2012		Sep. 30, 2011	Dec. 31, 2011	Sep. 30, 2012 Unsecured Letter of Credit Facility [Member]	Sep. 30, 2011 Unsecured Letter of Credit Facility [Member]	Sep. 30, 2012 Unsecured Letter of Credit Facility [Member] March 2013 [Member]	Sep. 30, 2012 Unsecured Letter of Credit Facility [Member] September 2013 [Member]	Sep. 30, 2012 Revolving Credit Facility [Member]	Sep. 30, 2012 Senior Note Due 10/14/2016 [Member]	Sep. 30, 2012 Line of Credit CoBank [Member]	Sep. 30, 2012 Senior Note [Member]	Dec. 31, 2011 Senior Note [Member]	Sep. 30, 2012 Debentures [Member]	Dec. 31, 2011 Debentures [Member]	Sep. 30, 2012 Subsidiary Senior Notes Due 12/1/2012 [Member]	Dec. 31, 2011 Subsidiary Senior Notes Due 12/1/2012 [Member]	Sep. 30, 2012 Senior unsecured notes due 2021 [Member]	Oct. 26, 2012 Senior unsecured notes due 2021 [Member]	Sep. 30, 2012 Senior notes due 2023 [Member]	Sep. 30, 2012 Senior notes due 2013 [Member]	Jun. 30, 2012 Senior notes due 2013 [Member]	Sep. 30, 2012 Senior notes due 2013 [Member]	Sep. 30, 2012 2014 Notes [Member]	Sep. 30, 2012 April 2015 Notes [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Senior Note Due 1/15/2013 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note Due 1/15/2013 [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Senior Note Due 5/1/2014 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note Due 5/1/2014 [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Senior Note Due 3/15/2015 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note Due 3/15/2015 [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Senior Note Due 4/15/2015 [Member]		Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note Due 4/15/2015 [Member]		Sep. 30, 2012 Senior Unsecured Debt [Member] Senior Note Due 4/15/2017 [Member]		Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note Due 4/15/2017 [Member]		Sep. 30, 2012 Senior Unsecured Debt [Member] Senior Note Due 10/1/2018 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note Due 10/1/2018 [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Senior Note Due 1/15/2023 [Member]		Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note Due 1/15/2023 [Member]		Sep. 30, 2012 Senior Unsecured Debt [Member] Senior Note Due 3/15/2019 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note Due 3/15/2019 [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Senior Note Due 4/15/2020 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note Due 4/15/2020 [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Senior Note Due 7/1/2021 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note Due 7/1/2021 [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Senior Note Due 4/15/2022 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note Due 4/15/2022 [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Senior Note Due 1/15/2027 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note Due 1/15/2027 [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Senior Note Due 2/15/2028 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note Due 2/15/2028 [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Senior Note Due 10/15/2029 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note Due 10/15/2029 [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Senior Note Due 8/15/2031 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note Due 8/15/2031 [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Debenture Due 11/1/2025 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Debenture Due 11/1/2025 [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Debenture Due 8/15/2026 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Debenture Due 8/15/2026 [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Debenture Due 10/1/2034 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Debenture Due 10/1/2034 [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Debenture Due 7/1/2035 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Debenture Due 7/1/2035 [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Debenture Due 10/1/2046 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Debenture Due 10/1/2046 [Member]	Sep. 30, 2012 Senior Unsecured Debt [Member] Senior Note Due 10/14/2016 [Member]		Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note Due 10/14/2016 [Member]		Sep. 30, 2012 Notes [Member]	Sep. 30, 2012 Rural Utilities Service Loan Contracts [Member]		Sep. 30, 2012 Senior Unsecured Debt [Member]		Sep. 30, 2012 Industrial Development Revenue Bonds [Member]
Long Term Debt [Roll Forward]
Long-term debt, beginning balance				$ 8,349,521,000									$ 575,000,000		$ 8,569,083,000	$ 8,039,774,000	$ 8,855,083,000	$ 8,325,774,000	$ 36,000,000	$ 36,000,000							$ 200,000,000	$ 450,500,000	$ 502,658,000	$ 580,724,000	$ 200,000,000	$ 600,000,000	$ 300,000,000	$ 300,000,000	$ 450,500,000	[1]	$ 500,000,000	[1]	$ 1,100,000,000	[1]	$ 1,100,000,000	[1]	$ 600,000,000	$ 600,000,000	$ 600,000,000	[1]	$ 0	[1]	$ 434,000,000	$ 434,000,000	$ 1,100,000,000	$ 1,100,000,000	$ 500,000,000	$ 0	$ 500,000,000	$ 500,000,000	$ 345,858,000	$ 345,858,000	$ 200,000,000	$ 200,000,000	$ 50,000,000	$ 50,000,000	$ 945,325,000	$ 945,325,000	$ 138,000,000	$ 138,000,000	$ 1,739,000	$ 1,739,000	$ 628,000	$ 628,000	$ 125,000,000	$ 125,000,000	$ 193,500,000	$ 193,500,000	$ 531,875,000	[2]	$ 575,000,000	[2]		$ 10,197,000		$ 8,325,774,000		$ 13,550,000
Payments				(571,472,000)																																																																												(781,000)		(570,691,000)		0
Borrowings				1,100,000,000																																																																												0		1,100,000,000		0
Long-term debt, ending balance	8,878,049,000			8,878,049,000									575,000,000		8,569,083,000	8,039,774,000	8,855,083,000	8,325,774,000	36,000,000	36,000,000							200,000,000	450,500,000	502,658,000	580,724,000	200,000,000	600,000,000	300,000,000	300,000,000	450,500,000	[1]	500,000,000	[1]	1,100,000,000	[1]	1,100,000,000	[1]	600,000,000	600,000,000	600,000,000	[1]	0	[1]	434,000,000	434,000,000	1,100,000,000	1,100,000,000	500,000,000	0	500,000,000	500,000,000	345,858,000	345,858,000	200,000,000	200,000,000	50,000,000	50,000,000	945,325,000	945,325,000	138,000,000	138,000,000	1,739,000	1,739,000	628,000	628,000	125,000,000	125,000,000	193,500,000	193,500,000	531,875,000	[2]	575,000,000	[2]		9,416,000		8,855,083,000		13,550,000
Less: Debt Discount	(23,905,000)			(23,905,000)			(49,664,000)
Less: Current Portion	(596,545,000)			(596,545,000)			(94,016,000)
Principal Outstanding	8,257,599,000			8,257,599,000			8,205,841,000
Interest Rate (in hundredths)	7.87%	[3]		7.87%	[3]																																																																											6.15%	[3]	7.88%	[3]	6.33%	[3]
Senior Notes [Abstract]
Principal Outstanding	8,878,049,000			8,878,049,000									575,000,000		8,569,083,000	8,039,774,000	8,855,083,000	8,325,774,000	36,000,000	36,000,000							200,000,000	450,500,000	502,658,000	580,724,000	200,000,000	600,000,000	300,000,000	300,000,000	450,500,000	[1]	500,000,000	[1]	1,100,000,000	[1]	1,100,000,000	[1]	600,000,000	600,000,000	600,000,000	[1]	0	[1]	434,000,000	434,000,000	1,100,000,000	1,100,000,000	500,000,000	0	500,000,000	500,000,000	345,858,000	345,858,000	200,000,000	200,000,000	50,000,000	50,000,000	945,325,000	945,325,000	138,000,000	138,000,000	1,739,000	1,739,000	628,000	628,000	125,000,000	125,000,000	193,500,000	193,500,000	531,875,000	[2]	575,000,000	[2]		9,416,000		8,855,083,000		13,550,000
Interest Rate (in hundredths)												0.625%					7.88%	7.93%	8.05%	8.05%	9.25%		7.125%	6.25%		6.25%	8.25%	7.875%	6.25%	6.25%	8.25%	8.25%	6.625%	6.625%	7.875%	[1]	7.875%	[1]	8.25%	[1]	8.25%	[1]	8.125%	8.125%	7.125%	[1]	0.00%	[1]	7.125%	7.125%	8.50%	8.50%	9.25%	0.00%	8.75%	8.75%	7.875%	7.875%	6.73%	6.73%	8.40%	8.40%	9.00%	9.00%	7.00%	7.00%	6.80%	6.80%	7.68%	7.68%	7.45%	7.45%	7.05%	7.05%	3.095%	[2]	3.175%	[2]
Aggregate principal amount of debt under registered offering																					500,000,000		600,000,000				500,000,000																																																				600,000,000
Issue price expressed as a percentage of principal amount (in hundredths)																					100.00%	100.00%
Net proceeds from offering																					489,600,000		588,100,000
Effective interest cost (in hundredths)																											10.855%
Aggregate principal amount agreed to be purchased																											400,000,000	49,500,000
Amount of consideration for purchase of notes																											446,000,000	54,000,000
Losses on early extinguishment of debt	245,000		0	71,063,000		0																		500,000	69,200,000	2,100,000
Debt instrument repurchase amount																								78,100,000		78,100,000
Credit Agreement [Abstract]
Repayment of the outstanding principal balance, quarterly installments amount														14,375,000
First payment date of the quarterly repayment of the outstanding principal balance														Mar. 31, 2012
Interest rate margin for Base Rate borrowings, minimum (in hundredths)														0.875%
Interest rate margin for Base Rate borrowings, maximum (in hundredths)														2.875%
Interest rate margin for LIBOR borrowings, minimum (in hundredths)														1.875%
Interest rate margin for LIBOR borrowings, maximum (in hundredths)														3.875%
Initial pricing for LIBOR based borrowings (in hundredths)														2.875%
Maximum permitted leverage ratio														4.5
Credit facilities [Abstract]
Interest Rate (in hundredths)												0.625%					7.88%	7.93%	8.05%	8.05%	9.25%		7.125%	6.25%		6.25%	8.25%	7.875%	6.25%	6.25%	8.25%	8.25%	6.625%	6.625%	7.875%	[1]	7.875%	[1]	8.25%	[1]	8.25%	[1]	8.125%	8.125%	7.125%	[1]	0.00%	[1]	7.125%	7.125%	8.50%	8.50%	9.25%	0.00%	8.75%	8.75%	7.875%	7.875%	6.73%	6.73%	8.40%	8.40%	9.00%	9.00%	7.00%	7.00%	6.80%	6.80%	7.68%	7.68%	7.45%	7.45%	7.05%	7.05%	3.095%	[2]	3.175%	[2]
Line of credit initiation date				Mar. 23, 2010
Line of credit facility expiration date				Jan. 01, 2014
Line of credit facility maximum borrowing capacity								40,000,000	190,000,000	20,000,000	20,000,000	750,000,000
Number of letters of credit								2
Exercised extension of commitment								100,000,000
Date that the Bank to exercise its option to extend the commitments								2012-09-20
Principal payments by year [Abstract]
Principal Payments 2012 (remaining three months)	50,470,000			50,470,000
Principal Payments 2013	560,550,000			560,550,000
Principal Payments 2014	257,916,000			257,916,000
Principal Payments 2015	808,442,000			808,442,000
Principal Payments 2016	345,466,000			345,466,000
Principal Payments 2017	$ 1,100,501,000			$ 1,100,501,000

[1] See Note 18 – Subsequent Events.

[2] Represents borrowings under the Credit Agreement with CoBank.

[3] Interest rate includes amortization of debt issuance costs and debt premiums or discounts. The interest rates at September 30, 2012 represent a weighted average of multiple issuances.