CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating revenues
Electric	$ 717,462	$ 749,461
Natural gas	328,494	373,203
Steam and other	11,885	12,786
Total operating revenues	1,057,841	1,135,450
Operating expenses
Electric fuel and purchased power	295,930	322,758
Cost of natural gas sold and transported	168,476	228,744
Cost of sales — steam and other	3,781	5,693
Operating and maintenance expenses	178,386	182,417
Demand side management program expenses	27,723	30,069
Depreciation and amortization	108,881	100,043
Taxes (other than income taxes)	51,474	50,326
Total operating expenses	834,651	920,050
Operating income	223,190	215,400
Other income, net	449	687
Allowance for funds used during construction — equity	4,318	2,806
Interest charges and financing costs
Interest charges — includes other financing costs of $1,739 and $1,505, respectively	45,748	43,090
Allowance for funds used during construction — debt	(1,610)	(1,098)
Total interest charges and financing costs	44,138	41,992
Income before income taxes	183,819	176,901
Income taxes	67,945	65,935
Net income	$ 115,874	$ 110,966