CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Operating revenues
Electric	$ 2,219,877	$ 2,036,829	$ 4,312,073	$ 3,973,611
Natural gas	341,321	221,313	1,010,917	842,348
Other	17,715	16,526	38,772	36,788
Total operating revenues	2,578,913	2,274,668	5,361,762	4,852,747
Operating expenses
Electric fuel and purchased power	1,011,044	854,373	1,936,087	1,718,353
Cost of natural gas sold and transported	188,765	89,759	628,140	507,705
Cost of sales — other	7,881	5,944	16,292	13,248
Operating and maintenance expenses	562,557	534,014	1,091,788	1,044,698
Conservation and demand side management program expenses	60,445	58,615	124,477	122,322
Depreciation and amortization	243,934	226,641	492,640	455,313
Taxes (other than income taxes)	102,051	99,632	215,478	205,256
Total operating expenses	2,176,677	1,868,978	4,504,902	4,066,895
Operating income	402,236	405,690	856,860	785,852
Other income, net	413	728	4,335	4,465
Equity earnings of unconsolidated subsidiaries	7,529	7,502	15,106	14,660
Allowance for funds used during construction — equity	22,109	15,194	41,863	28,644
Interest charges and financing costs
Interest charges — includes other financing costs of $12,229, $6,036, $18,038 and $12,116, respectively	146,828	151,921	286,441	303,751
Allowance for funds used during construction — debt	(10,316)	(7,683)	(19,074)	(14,290)
Total interest charges and financing costs	136,512	144,238	267,367	289,461
Income from continuing operations before income taxes	295,775	284,876	650,797	544,160
Income taxes	98,893	101,801	217,327	177,316
Income from continuing operations	196,882	183,075	433,470	366,844
(Loss) income from discontinued operations, net of tax	(25)	(15)	(43)	109
Net income	$ 196,857	$ 183,060	$ 433,427	$ 366,953
Weighted average common shares outstanding:
Basic (in shares)	497,747	487,717	493,786	487,538
Diluted (in shares)	498,036	488,017	494,303	488,006
Earnings per average common share:
Basic (in dollars per share)	$ 0.40	$ 0.38	$ 0.88	$ 0.75
Diluted (in dollars per share)	$ 0.40	$ 0.38	$ 0.88	$ 0.75
Cash dividends declared per common share (in dollars per share)	$ 0.28	$ 0.27	$ 0.55	$ 0.53