Discontinued Operations Balance Sheet and Income Statement (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Assets of Disposal Group, Including Discontinued Operation [Abstract]
Cash	$ 11,807,000		$ 11,807,000		$ 3,032,000
Accounts receivable	50,285,000		50,285,000		107,849,000
Inventories	39,950,000		39,950,000		41,268,000
Oil and gas properties					348,379,000
Less accumulated depreciation, depletion and amortization	(624,704,000)		(624,704,000)		(301,609,000)
Utility plant	1,517,534,000		1,517,534,000		1,491,433,000
Less accumulated depreciation					(605,924,000)
Other property, net	40,000		40,000		206,000
Other current assets	16,462,000		16,462,000		29,458,000
Other long-term assets	142,672,000		142,672,000		128,780,000
Total assets held for sale	1,154,046,000		1,154,046,000		1,242,872,000
Total assets held for sale
Accounts payable	(42,674,000)		(42,674,000)		(50,396,000)
Royalty payable	(1,284,000)		(1,284,000)		(1,419,000)
Accrued taxes	(29,337,000)		(29,337,000)		(28,027,000)
Long-term debt due within one year	(50,000,000)		(50,000,000)
Notes payable to banks					(50,000,000)
Other current liabilities	(108,635,000)		(108,635,000)		(105,413,000)
Other long-term liabilities	(335,371,000)		(335,371,000)		(346,392,000)
Long-term debt	(199,830,000)		(199,830,000)		(249,923,000)
Total liabilities held for sale	(767,131,000)		(767,131,000)		(831,570,000)
Total net assets held for sale	386,915,000		386,915,000		411,302,000
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Natural gas distribution revenues	93,873,000	104,514,000	357,774,000	342,199,000
Oil and natural gas revenues	390,000	18,562,000	5,211,000	37,225,000
Total revenues	94,263,000	123,076,000	362,985,000	379,424,000
Pretax income (loss) from discontinued operations	(7,797,000)	967,000	54,519,000	78,775,000
Income tax expense (benefit)	(2,998,000)	322,000	20,599,000	29,857,000
Income (Loss) From Discontinued Operations	(4,799,000)	645,000	33,920,000	48,918,000
Loss on disposal of discontinued operations	0	0	(1,667,000)	0
Income tax benefit	0	0	(617,000)	0
Loss on Disposal of Discontinued Operations	0	0	(1,050,000)	0
Total Income (Loss) From Discontinued Operations	(4,799,000)	645,000	32,870,000	48,918,000
Diluted Earnings Per Average Common Share
Income (Loss) from Discontinued Operations (in dollars per share)	$ (0.07)	$ 0.01	$ 0.46	$ 0.67
Loss on Disposal of Discontinued Operations (in dollars per share)	$ 0.00	$ 0.00	$ (0.01)	$ 0.00
Total Income (Loss) From Discontinued Operations (in dollars per share)	$ (0.07)	$ 0.01	$ 0.45	$ 0.67
Basic Earnings Per Average Common Share
Income (Loss) from Discontinued Operations (in dollars per share)	$ (0.07)	$ 0.01	$ 0.46	$ 0.68
Loss on Disposal of Discontinued Operations (in dollars per share)	$ 0.00	$ 0.00	$ (0.01)	$ 0.00
Total Income (Loss) From Discontinued Operations (in dollars per share)	$ (0.07)	$ 0.01	$ 0.45	$ 0.68
Adjustment for affiliated companies receivables		13,200,000		13,200,000	4,700,000
Reclassification from accrued taxes to other current assets		7,900,000		7,900,000	1,600,000
Reclassification from accrued taxes to other current liabilities					500,000
Alabama Gas Corporation
Assets of Disposal Group, Including Discontinued Operation [Abstract]
Cash	11,807,000		11,807,000		3,032,000
Accounts receivable	50,285,000		50,285,000		103,748,000
Inventories	39,950,000		39,950,000		41,200,000
Oil and gas properties					0
Less accumulated depreciation, depletion and amortization	(624,704,000)		(624,704,000)		0
Utility plant	1,517,534,000		1,517,534,000		1,491,433,000
Less accumulated depreciation					(605,924,000)
Other property, net	40,000		40,000		41,000
Other current assets	16,462,000		16,462,000		29,458,000
Other long-term assets	142,672,000		142,672,000		128,780,000
Total assets held for sale	1,154,046,000		1,154,046,000		1,191,768,000
Total assets held for sale
Accounts payable	(38,646,000)		(38,646,000)		(48,653,000)
Royalty payable	0		0		0
Accrued taxes	(29,337,000)		(29,337,000)		(28,027,000)
Long-term debt due within one year	(50,000,000)		(50,000,000)
Notes payable to banks					(50,000,000)
Other current liabilities	(108,633,000)		(108,633,000)		(105,013,000)
Other long-term liabilities	(335,369,000)		(335,369,000)		(331,409,000)
Long-term debt	(199,830,000)		(199,830,000)		(249,923,000)
Total liabilities held for sale	(761,815,000)		(761,815,000)		(813,025,000)
Total net assets held for sale	392,231,000		392,231,000		378,743,000
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Total Income (Loss) From Discontinued Operations	(4,896,000)	(1,808,000)	34,949,000	44,467,000
Black Warrior Basin
Assets of Disposal Group, Including Discontinued Operation [Abstract]
Cash	0		0		0
Accounts receivable	0		0		2,829,000
Inventories	0		0		0
Oil and gas properties					0
Less accumulated depreciation, depletion and amortization	0		0
Utility plant	0		0		0
Less accumulated depreciation					0
Other property, net	0		0		0
Other current assets	0		0		0
Other long-term assets	0		0		0
Total assets held for sale	0		0		2,829,000
Total assets held for sale
Accounts payable	(2,172,000)		(2,172,000)		(1,732,000)
Royalty payable	0		0		(550,000)
Accrued taxes	0		0		0
Long-term debt due within one year	0		0
Notes payable to banks					0
Other current liabilities	0		0		(379,000)
Other long-term liabilities	0		0		0
Long-term debt	0		0		0
Total liabilities held for sale	(2,172,000)		(2,172,000)		(2,661,000)
Total net assets held for sale	(2,172,000)		(2,172,000)		168,000
North Louisiana/East Texas
Assets of Disposal Group, Including Discontinued Operation [Abstract]
Cash	0		0		0
Accounts receivable	0		0		1,272,000
Inventories	0		0		68,000
Oil and gas properties					348,379,000
Less accumulated depreciation, depletion and amortization	0		0		(301,609,000)
Utility plant	0		0		0
Less accumulated depreciation					0
Other property, net	0		0		165,000
Other current assets	0		0		0
Other long-term assets	0		0		0
Total assets held for sale	0		0		48,275,000
Total assets held for sale
Accounts payable	(1,856,000)		(1,856,000)		(11,000)
Royalty payable	(1,284,000)		(1,284,000)		(869,000)
Accrued taxes	0		0		0
Long-term debt due within one year	0		0
Notes payable to banks					0
Other current liabilities	(2,000)		(2,000)		(21,000)
Other long-term liabilities	(2,000)		(2,000)		(14,983,000)
Long-term debt	0		0		0
Total liabilities held for sale	(3,144,000)		(3,144,000)		(15,884,000)
Total net assets held for sale	$ (3,144,000)		$ (3,144,000)		$ 32,391,000