CONSOLIDATED STATEMENTS OF EARNINGS - USD ($) $ in Thousands, shares in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Revenues:
Gas	$ 194,000	$ 181,200	$ 202,600
Electric	206,200	196,100	218,000
Other	6,000	6,100	6,200
Total Operating Revenues	406,200	383,400	426,800
Operating Expenses:
Cost of Gas Sales	84,300	77,600	100,700
Cost of Electric Sales	114,000	108,000	132,500
Operation and Maintenance	70,200	66,300	67,100
Depreciation and Amortization	46,900	46,600	45,700
Taxes Other Than Income Taxes	21,100	19,600	17,700
Total Operating Expenses	336,500	318,100	363,700
Operating Income	69,700	65,300	63,100
Interest Expense, net	23,100	22,500	21,900
Other Expense (Income), net	100	300	(500)
Income Before Income Taxes	46,500	42,500	41,700
Income Taxes	17,537	15,354	15,443
Net Income Applicable to Common Shares	$ 29,000	$ 27,100	$ 26,300
Earnings per Common Share-Basic and Diluted	$ 2.06	$ 1.94	$ 1.89
Weighted Average Common Shares Outstanding-(Basic and Diluted)	14.1	14.0	13.9