CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Operating revenues
Electric	$ 747,882	$ 714,651	$ 1,469,230	$ 1,396,930
Natural gas	209,296	147,398	593,220	530,402
Steam and other	9,251	7,452	21,436	18,221
Total operating revenues	966,429	869,501	2,083,886	1,945,553
Operating expenses
Electric fuel and purchased power	322,787	294,698	642,668	605,597
Cost of natural gas sold and transported	109,697	57,091	359,317	313,968
Cost of sales — steam and other	4,008	2,928	8,813	7,095
Operating and maintenance expenses	188,152	180,100	361,193	348,482
Demand side management program expenses	32,938	29,348	66,059	58,792
Depreciation and amortization	89,079	80,151	178,629	163,740
Taxes (other than income taxes)	36,093	32,875	71,233	66,663
Total operating expenses	782,754	677,191	1,687,912	1,564,337
Operating income	183,675	192,310	395,974	381,216
Other income, net	1,322	1,550	2,899	2,582
Allowance for funds used during construction — equity	6,791	3,548	12,714	6,274
Interest charges and financing costs
Interest charges — includes other financing costs of $1,723, $1,790, $3,371, and $3,580, respectively	43,231	48,074	84,619	96,365
Allowance for funds used during construction — debt	(3,100)	(1,534)	(5,251)	(2,695)
Total interest charges and financing costs	40,131	46,540	79,368	93,670
Income before income taxes	151,657	150,868	332,219	296,402
Income taxes	54,358	55,461	118,315	107,710
Net income	$ 97,299	$ 95,407	$ 213,904	$ 188,692