CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Operating revenues
Electric	$ 734,264	$ 721,348
Natural gas	456,337	383,924
Steam and other	12,942	12,185
Total operating revenues	1,203,543	1,117,457
Operating expenses
Electric fuel and purchased power	334,470	319,881
Cost of natural gas sold and transported	309,805	249,620
Cost of sales — steam and other	4,978	4,805
Operating and maintenance expenses	175,524	173,041
Demand side management program expenses	35,195	33,121
Depreciation and amortization	93,316	89,550
Taxes (other than income taxes)	41,818	35,140
Total operating expenses	995,106	905,158
Operating income	208,437	212,299
Other income, net	797	1,577
Allowance for funds used during construction — equity	11,430	5,923
Interest charges and financing costs
Interest charges — includes other financing costs of $1,720 and $1,648, respectively	43,972	41,388
Allowance for funds used during construction — debt	(4,208)	(2,151)
Total interest charges and financing costs	39,764	39,237
Income before income taxes	180,900	180,562
Income taxes	62,497	63,957
Net income	$ 118,403	$ 116,605