CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Operating Revenues	$ 141,592	$ 134,598	$ 138,077
Operating Expenses:
Operations and Maintenance	70,796	67,980	71,570
Depreciation	18,472	16,716	15,037
Other Taxes	14,904	14,382	14,328
Total Operating Expenses	104,172	99,078	100,935
Operating Income	37,420	35,520	37,142
Other Income (Expense):
Allowance for Funds Used During Construction	4,016	3,146	1,362
Other Income (Expense), net	363	(654)	1,630
Total Other Income, net	4,379	2,492	2,992
Interest Charges	7,493	7,264	6,758
Income before Income Taxes	34,306	30,748	33,376
Income Taxes	(4,119)	(3,140)	924
Net Income	38,425	33,888	32,452
Preferred Stock Dividend Requirements	120	132	144
Earnings Applicable to Common Stock	$ 38,305	$ 33,756	$ 32,308
Earnings per share of Common Stock:
Basic	$ 2.19	$ 2.02	$ 1.97
Diluted	$ 2.18	$ 2.01	$ 1.96
Average Number of Common Shares Outstanding :
Basic	17,459	16,685	16,384
Diluted	17,574	16,829	16,540