CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating revenues
Electric	$ 849,946	$ 834,998	$ 829,748
Natural gas	106,157	120,147	169,629
Other	1,130	1,396	1,085
Total operating revenues	957,233	956,541	1,000,462
Operating expenses
Electric fuel and purchased power, non-affiliates	15,574	10,795	19,595
Purchased power, affiliates	413,615	419,028	425,471
Cost of natural gas sold and transported	54,436	70,988	114,250
Operating and maintenance expenses	194,927	179,413	191,213
Conservation program expenses	12,645	11,695	11,537
Depreciation and amortization	98,294	91,245	79,654
Taxes (other than income taxes)	27,814	28,181	27,114
Loss on Monticello life cycle management/extended power uprate project	0	5,237	0
Total operating expenses	817,305	816,582	868,834
Operating income	139,928	139,959	131,628
Other income, net	461	883	270
Allowance for funds used during construction — equity	4,277	7,253	7,060
Interest charges and financing costs
Interest charges — includes other financing costs of $1,854, $1,738, and $1,570, respectively	34,452	32,731	29,273
Public Utilities, Allowance For Funds Used During Construction, Capitalized Cost Of Debt	(1,823)	(3,510)	(3,360)
Total interest charges and financing costs	32,629	29,221	25,913
Income before income taxes	112,037	118,874	113,045
Income taxes	42,902	44,238	42,403
Net income	$ 69,135	$ 74,636	$ 70,642