CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Revenues
Retail	$ 1,040,682	$ 989,580	$ 1,021,543
Wholesale	174,742	117,341	167,020
Other	125,511	128,074	117,981
Total Operating Revenues	1,340,935	1,234,995	1,306,544
Operating Expenses
Fuel	285,551	289,862	305,559
Purchased Power	136,425	85,354	124,764
Transmission and Other PPFAC Recoverable Costs	36,239	23,781	24,798
Increase (Decrease) to Reflect PPFAC Recovery Treatment	(32,660)	21,064	39,787
Total Fuel and Purchased Power	425,555	420,061	494,908
Operations and Maintenance	360,302	353,905	345,356
Depreciation	152,874	146,097	138,093
Amortization	22,255	22,498	19,261
Taxes Other Than Income Taxes	53,623	49,303	49,623
Total Operating Expenses	1,014,609	991,864	1,047,241
Operating Income	326,326	243,131	259,303
Other Income (Deductions)
Interest Income	742	111	93
Other Income	14,128	5,636	6,647
Other Expense	(3,344)	(3,019)	(2,833)
Appreciation (Depreciation) in Value of Investments	2,791	2,147	(142)
Total Other Income (Deductions)	14,317	4,875	3,765
Interest Expense
Long-Term Debt	62,018	62,015	61,159
Capital Leases	2,554	3,356	3,994
Other Interest Expense	718	531	1,134
Interest Capitalized	(2,078)	(1,710)	(2,732)
Total Interest Expense	63,212	64,192	63,555
Income Before Income Taxes	277,431	183,814	199,513
Income Tax Expense	100,763	59,376	71,719
Net Income	$ 176,668	$ 124,438	$ 127,794