CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating revenues
Electric	$ 8,766,593	$ 8,451,845	$ 7,704,723
Natural gas	1,811,926	1,782,582	1,865,703
Other	76,251	76,520	73,877
Total operating revenues	10,654,770	10,310,947	9,644,303
Operating expenses
Electric fuel and purchased power	3,991,786	4,010,660	3,672,490
Cost of natural gas sold and transported	1,163,890	1,162,926	1,266,440
Cost of sales - other	30,391	29,540	22,107
Operating and maintenance expenses	2,140,289	2,057,249	1,908,097
Conservation and demand side management program expenses	281,378	239,827	182,112
Depreciation and amortization	890,619	858,882	818,052
Taxes (other than income taxes)	374,815	331,894	306,433
Total operating expenses	8,873,168	8,690,978	8,175,731
Operating income	1,781,602	1,619,969	1,468,572
Other income, net	9,255	31,143	9,771
Equity earnings of unconsolidated subsidiaries	30,527	29,948	24,664
Allowance for funds used during construction - equity	51,223	56,152	75,686
Interest charges and financing costs
Interest charges - includes other financing costs of $24,019, $20,638, and $20,162, respectively	591,098	577,291	561,654
Allowance for funds used during construction - debt	(28,181)	(28,670)	(39,799)
Total interest charges and financing costs	562,917	548,621	521,855
Income from continuing operations before income taxes	1,309,690	1,188,591	1,056,838
Income taxes	468,316	436,635	371,314
Income from continuing operations	841,374	751,956	685,524
Income (loss) from discontinued operations, net of tax	(202)	3,878	(4,637)
Net income	841,172	755,834	680,887
Dividend requirements on preferred stock	3,534	4,241	4,241
Premium on redemption of preferred stock	3,260	0	0
Earnings available to common shareholders	$ 834,378	$ 751,593	$ 676,646
Weighted average common shares outstanding:
Basic (in shares)	485,039	462,052	456,433
Diluted (in shares)	485,615	463,391	457,139
Earnings per average common share - basic:
Income from continuing operations (in dollars per share)	$ 1.72	$ 1.62	$ 1.49
Income (loss) from discontinued operations (in dollars per share)	$ 0	$ 0.01	$ (0.01)
Earnings per share (in dollars per share)	$ 1.72	$ 1.63	$ 1.48
Earnings per average common share - diluted:
Income from continuing operations (in dollars per share)	$ 1.72	$ 1.61	$ 1.49
Income (loss) from discontinued operations (in dollars per share)	$ 0	$ 0.01	$ (0.01)
Earnings per share (in dollars per share)	$ 1.72	$ 1.62	$ 1.48
Cash dividends declared per common share (in dollars per share)	$ 1.03	$ 1.00	$ 0.97