CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Revenues
Retail	$ 989,580	$ 1,021,543	$ 970,145
Wholesale	117,341	167,020	158,323
Other	128,074	117,981	141,433
Total Operating Revenues	1,234,995	1,306,544	1,269,901
Operating Expenses
Fuel	289,862	305,559	297,537
Purchased Power	85,354	124,764	152,922
Transmission and Other PPFAC Recoverable Costs	23,781	24,798	18,179
Increase (Decrease) to Reflect PPFAC Recovery Treatment	21,064	39,787	(11,194)
Total Fuel and Purchased Power	420,061	494,908	457,444
Operations and Maintenance	353,905	345,356	378,877
Depreciation	146,097	138,093	126,520
Amortization	22,498	19,261	28,567
Taxes Other Than Income Taxes	49,303	49,623	47,805
Total Operating Expenses	991,864	1,047,241	1,039,213
Operating Income	243,131	259,303	230,688
Other Income (Deductions)
Other Income	111	93	208
Other Income	5,636	6,647	8,598
Other Expense	(3,019)	(2,833)	(12,735)
Appreciation (Depreciation) in Value of Investments	2,147	(142)	1,371
Total Other Income (Deductions)	4,875	3,765	(2,558)
Interest Expense
Long-Term Debt	62,015	61,159	60,577
Capital Leases	3,356	3,994	10,249
Other Interest Expense	531	1,134	810
Interest Capitalized	(1,710)	(2,732)	(3,755)
Total Interest Expense	64,192	63,555	67,881
Income Before Income Taxes	183,814	199,513	160,249
Income Tax Expense	59,376	71,719	57,911
Net Income	$ 124,438	$ 127,794	$ 102,338