CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Operating Revenues	$ 134,598	$ 138,077	$ 130,775
Operating Expenses:
Operations and Maintenance	67,980	71,570	65,490
Depreciation	16,716	15,037	13,922
Other Taxes	14,382	14,328	13,565
Total Operating Expenses	99,078	100,935	92,977
Operating Income	35,520	37,142	37,798
Other Income (Expense):
Allowance for Funds Used During Construction	3,146	1,362	702
Other Income (Expense), net	(654)	1,630	915
Total Other Income, net	2,492	2,992	1,617
Interest Charges	7,264	6,758	5,506
Income before Income Taxes	30,748	33,376	33,909
Income Taxes	(3,140)	924	11,100
Net Income	33,888	32,452	22,809
Preferred Stock Dividend Requirements	132	144	144
Earnings Applicable to Common Stock	$ 33,756	$ 32,308	$ 22,665
Earnings per share of Common Stock:
Basic	$ 2.02	$ 1.97	$ 1.39
Diluted	$ 2.01	$ 1.96	$ 1.38
Average Number of Common Shares Outstanding :
Basic	16,685	16,384	16,330
Diluted	16,829	16,540	16,486