CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating revenues
Electric	$ 834,998	$ 829,748	$ 789,168
Natural gas	120,147	169,629	132,867
Other	1,396	1,085	1,003
Total operating revenues	956,541	1,000,462	923,038
Operating expenses
Electric fuel and purchased power, non-affiliates	10,795	19,595	18,129
Purchased power, affiliates	419,028	425,471	416,173
Cost of natural gas sold and transported	70,988	114,250	81,572
Operating and maintenance expenses	179,413	191,213	175,522
Conservation program expenses	11,695	11,537	12,333
Depreciation and amortization	91,245	79,654	76,897
Taxes (other than income taxes)	28,181	27,114	25,231
Loss on Monticello LCM/EPU project	5,237	0	0
Total operating expenses	816,582	868,834	805,857
Operating income	139,959	131,628	117,181
Other income, net	883	270	253
Allowance for funds used during construction — equity	7,253	7,060	4,259
Interest charges and financing costs
Interest charges — includes other financing costs of $1,738, $1,570, and $1,538, respectively	32,731	29,273	27,797
Public Utilities, Allowance For Funds Used During Construction, Capitalized Cost Of Debt	(3,510)	(3,360)	(1,981)
Total interest charges and financing costs	29,221	25,913	25,816
Income before income taxes	118,874	113,045	95,877
Income taxes	44,238	42,403	36,409
Net income	$ 74,636	$ 70,642	$ 59,468