CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating revenues
Electric	$ 711,388	$ 717,462
Natural gas	356,136	328,494
Steam and other	13,010	11,885
Total operating revenues	1,080,534	1,057,841
Operating expenses
Electric fuel and purchased power	288,827	295,930
Cost of natural gas sold and transported	196,402	168,476
Cost of sales — steam and other	4,386	3,781
Operating and maintenance expenses	185,601	178,386
Demand side management program expenses	28,104	27,723
Depreciation and amortization	114,994	108,881
Taxes (other than income taxes)	49,798	51,474
Total operating expenses	868,112	834,651
Operating income	212,422	223,190
Other income, net	3,717	449
Allowance for funds used during construction — equity	4,608	4,318
Interest charges and financing costs
Interest charges — includes other financing costs of $1,521 and $1,739, respectively	45,882	45,748
Allowance for funds used during construction — debt	(1,906)	(1,610)
Total interest charges and financing costs	43,976	44,138
Income before income taxes	176,771	183,819
Income taxes	65,225	67,945
Net income	$ 111,546	$ 115,874