Long-Term Debt (Details) (USD $)	3 Months Ended		6 Months Ended					6 Months Ended	3 Months Ended	6 Months Ended				3 Months Ended	6 Months Ended																																																			6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Jun. 30, 2012 Unsecured Letter of Credit Facility [Member]	Sep. 20, 2011 Unsecured Letter of Credit Facility [Member]	Jun. 30, 2012 Revolving Credit Facility [Member]	Jun. 30, 2012 Senior Note Due 1/15/2013 [Member]	Jun. 30, 2012 Line of Credit CoBank [Member]	Jun. 30, 2012 Senior unsecured notes due 2021 [Member]	Jun. 30, 2012 2014 Notes [Member]	Jun. 30, 2012 April 2015 Notes [Member]	Jun. 30, 2012 Notes [Member]	Jun. 30, 2012 Rural Utilities Service Loan Contracts [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Senior Note [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 1/15/2013 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 1/15/2013 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 5/1/2014 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 5/1/2014 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 3/15/2015 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 3/15/2015 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 4/15/2015 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 4/15/2015 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 4/15/2017 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 4/15/2017 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 10/1/2018 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 10/1/2018 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 3/15/2019 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 3/15/2019 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 4/15/2020 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 4/15/2020 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 7/1/2021 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 7/1/2021 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 4/15/2022 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 4/15/2022 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 1/15/2027 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 1/15/2027 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 2/15/2028 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 2/15/2028 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 10/15/2029 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 10/15/2029 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 8/15/2031 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 8/15/2031 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 10/14/2016 [Member]		Dec. 31, 2011 Senior Unsecured Debt [Member] Senior Note [Member] Senior Note Due 10/14/2016 [Member]		Jun. 30, 2012 Senior Unsecured Debt [Member] Debentures [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Debentures [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Debentures [Member] Debenture Due 11/1/2025 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Debentures [Member] Debenture Due 11/1/2025 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Debentures [Member] Debenture Due 8/15/2026 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Debentures [Member] Debenture Due 8/15/2026 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Debentures [Member] Debenture Due 10/1/2034 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Debentures [Member] Debenture Due 10/1/2034 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Debentures [Member] Debenture Due 7/1/2035 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Debentures [Member] Debenture Due 7/1/2035 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Debentures [Member] Debenture Due 10/1/2046 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Debentures [Member] Debenture Due 10/1/2046 [Member]	Jun. 30, 2012 Senior Unsecured Debt [Member] Subsidiary Senior Notes Due 12/1/2012 [Member]	Dec. 31, 2011 Senior Unsecured Debt [Member] Subsidiary Senior Notes Due 12/1/2012 [Member]	Jun. 30, 2012 Industrial Development Revenue Bonds [Member]
Long Term Debt [Roll Forward]
Long-term debt, beginning balance			$ 8,349,521,000									$ 200,000,000	$ 450,500,000		$ 10,197,000	$ 8,325,774,000		$ 7,794,626,000	$ 7,830,907,000	$ 522,693,000	$ 580,724,000	$ 200,000,000	$ 600,000,000	$ 300,000,000	$ 300,000,000	$ 450,500,000	$ 500,000,000	$ 1,100,000,000	$ 1,100,000,000	$ 600,000,000	$ 600,000,000	$ 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	$ 546,250,000	[1]	$ 575,000,000	[1]	$ 458,867,000	$ 458,867,000	$ 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	$ 36,000,000	$ 36,000,000	$ 13,550,000
Payments			(536,968,000)												(687,000)	(536,281,000)																																																		0
Borrowings			500,000,000												0	500,000,000																																																		0
Long-term debt, ending balance	8,312,553,000		8,312,553,000									200,000,000	450,500,000		9,510,000	8,289,493,000		7,794,626,000	7,830,907,000	522,693,000	580,724,000	200,000,000	600,000,000	300,000,000	300,000,000	450,500,000	500,000,000	1,100,000,000	1,100,000,000	600,000,000	600,000,000	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	546,250,000	[1]	575,000,000	[1]	458,867,000	458,867,000	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	36,000,000	36,000,000	13,550,000
Less: Debt Discount	(25,461,000)		(25,461,000)		(49,664,000)
Less: Current Portion	(616,575,000)		(616,575,000)		(94,016,000)
Principal Outstanding	7,670,517,000		7,670,517,000		8,205,841,000
Interest Rate (in hundredths)	7.90%		7.90%												6.15%	7.90%																																																		6.33%
Senior Notes [Abstract]
Principal Outstanding	8,312,553,000		8,312,553,000									200,000,000	450,500,000		9,510,000	8,289,493,000		7,794,626,000	7,830,907,000	522,693,000	580,724,000	200,000,000	600,000,000	300,000,000	300,000,000	450,500,000	500,000,000	1,100,000,000	1,100,000,000	600,000,000	600,000,000	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	546,250,000	[1]	575,000,000	[1]	458,867,000	458,867,000	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	36,000,000	36,000,000	13,550,000
Interest Rate (in hundredths)								0.625%			9.25%	8.25%	7.875%			7.90%	7.93%			6.25%	6.25%	8.25%	8.25%	6.625%	6.625%	7.875%	7.875%	8.25%	8.25%	8.125%	8.125%	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%	3.115%	[1]	3.175%	[1]			7.00%	7.00%	6.80%	6.80%	7.68%	7.68%	7.45%	7.45%	7.05%	7.05%	8.05%	8.05%
Aggregate principal amount of debt under registered offering											500,000,000			500,000,000
Issue price expressed as a percentage of principal amount (in hundredths)											100.00%
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	70,818,000	0	70,818,000	0					1,600,000					69,200,000
Debt instrument repurchase amount									58,000,000
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										2012-03-31
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%			9.25%	8.25%	7.875%			7.90%	7.93%			6.25%	6.25%	8.25%	8.25%	6.625%	6.625%	7.875%	7.875%	8.25%	8.25%	8.125%	8.125%	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%	3.115%	[1]	3.175%	[1]			7.00%	7.00%	6.80%	6.80%	7.68%	7.68%	7.45%	7.45%	7.05%	7.05%	8.05%	8.05%
Line of credit initiation date								2010-03-23
Line of credit facility expiration date								2014-01-01
Line of credit facility maximum borrowing capacity						100,000,000	190,000,000	750,000,000
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 six months)	64,939,000		64,939,000
Principal Payments 2013	580,585,000		580,585,000
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] Represents borrowings under the Credit Agreement with CoBank.