Consolidated Statements of Income (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Operating revenues:
Electric, natural gas distribution and pipeline and energy services	$ 1,343,714,000		$ 1,359,028,000		$ 1,504,269,000
Exploration and production, construction materials and contracting, construction services, and other	2,706,778,000		2,550,667,000		2,672,232,000
Total operating revenues	4,050,492,000		3,909,695,000		4,176,501,000
Operating expenses:
Fuel and purchased power	64,485,000		63,065,000		65,717,000
Purchased natural gas sold	572,187,000		567,806,000		739,678,000
Operation and maintenance:
Electric, natural gas distribution and pipeline and energy services	275,866,000		291,524,000		263,869,000
Exploration and production, construction materials and contracting, construction services, and other	2,215,269,000		2,084,377,000		2,143,195,000
Depreciation, depletion and amortization	343,395,000		328,843,000		330,542,000
Taxes, other than income	172,923,000		163,353,000		166,597,000
Noncash write-down of natural gas and oil properties	0		0		620,000,000
Total operating expenses	3,644,125,000		3,498,968,000		4,329,598,000
Operating income (loss)	406,367,000		410,727,000		(153,097,000)
Earnings from equity method investments	4,693,000		30,816,000		8,499,000
Other income	6,520,000		8,018,000		9,331,000
Interest expense	81,354,000		83,011,000		84,099,000
Income (loss) before income taxes	336,226,000		366,550,000		(219,366,000)
Income taxes	110,274,000		122,530,000		(96,092,000)
Income (loss) from continuing operations	225,952,000		244,020,000		(123,274,000)
Income (loss) from discontinued operations, net of tax	(12,926,000)	[1]	(3,361,000)	[1]	0	[1]
Net income (loss)	213,026,000		240,659,000		(123,274,000)
Dividends on preferred stocks	685,000		685,000		685,000
Earnings (loss) on common stock	$ 212,341,000		$ 239,974,000		$ (123,959,000)
Earnings (loss) per common share - basic:
Earnings (Loss) Before Discontinued Operations	$ 1.19		$ 1.29		$ (0.67)
Discontinued Operations, Net of Tax	$ (0.07)		$ (0.01)		$ 0.00
Earnings (Loss) Per Common Share - Basic	$ 1.12		$ 1.28		$ (0.67)
Earnings (loss) per common share - diluted:
Earnings (Loss) Before Discontinued Operations	$ 1.19		$ 1.29		$ (0.67)
Discontinued Operations, Net of Tax	$ (0.07)		$ (0.02)		$ 0.00
Earnings (Loss) Per Common Share - Diluted	$ 1.12		$ 1.27		$ (0.67)
Dividends per common share (in dollars per share)	$ 0.6550		$ 0.6350		$ 0.6225
Weighted average common shares outstanding - basic	188,763		188,137		185,175	[2]
Weighted Average Common Shares Outstanding - Diluted	188,905		188,229		185,175	[2]

[1] Reflected in the Other category.

[2] Due to the loss on common stock, 825 outstanding stock options, 18 restricted stock grants and 656 performance share awards were excluded from the computation of diluted loss per common share as their effect was antidilutive.