CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues
Electric	$ 921,093	$ 1,037,053	$ 1,011,595
Gas	270,916	268,599	245,652
Total Revenues	1,192,009	1,305,652	1,257,247
Operating Expenses
Cost of sales	272,883	410,349	400,973
Operating, general and administrative	307,119	294,803	293,863
Property and other taxes	171,259	162,614	148,098
Depreciation and depletion	174,476	166,137	159,336
Total Operating Expenses	925,737	1,033,903	1,002,270
Operating Income	266,272	271,749	254,977
Interest Expense, net	(91,988)	(92,263)	(94,970)
Other Income (Expense), net	3,966	(3,415)	(3,482)
Income Before Income Taxes	178,250	176,071	156,525
Income Tax Benefit (Expense)	18,710	(13,368)	7,647
Net Income	$ 196,960	$ 162,703	$ 164,172
Average Common Shares Outstanding	49,984,562	48,557,599	48,298,896
Basic Earnings per Average Common Share	$ 3.94	$ 3.35	$ 3.40
Diluted Earnings per Average Common Share	$ 3.92	$ 3.34	$ 3.39