CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating revenues
Electric	$ 721,348	$ 682,279
Natural gas	383,924	383,004
Steam and other	12,185	10,769
Total operating revenues	1,117,457	1,076,052
Operating expenses
Electric fuel and purchased power	319,881	310,899
Cost of natural gas sold and transported	249,620	256,877
Cost of sales - steam and other	4,805	4,167
Operating and maintenance expenses	173,041	168,382
Demand side management program expenses	33,121	29,444
Depreciation and amortization	89,550	83,589
Taxes (other than income taxes)	35,140	33,788
Total operating expenses	905,158	887,146
Operating income	212,299	188,906
Other income, net	1,577	1,032
Allowance for funds used during construction - equity	5,923	2,726
Interest charges and financing costs
Interest charges - includes other financing costs of $1,648 and $1,790, respectively	41,388	48,291
Allowance for funds used during construction - debt	(2,151)	(1,161)
Total interest charges and financing costs	39,237	47,130
Income before income taxes	180,562	145,534
Income taxes	63,957	52,249
Net income	$ 116,605	$ 93,285