Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Revenues
Regulated Energy	$ 352,746	$ 343,006	$ 345,281
Unregulated Energy	152,526	154,151	161,905
Other	(17,074)	(17,552)	(16,870)
Total operating revenues	488,198	479,605	490,316
Operating Expenses
Regulated Energy cost of sales	91,994	102,803	121,828
Unregulated Energy and other cost of sales	45,944	51,698	68,341
Operations	142,055	137,845	132,523
Maintenance	15,587	15,679	14,387
Gain from a settlement	(130)	(130)	(130)
Depreciation and amortization	58,117	45,424	40,220
Other taxes	21,908	20,001	18,303
Total operating expenses	375,475	373,320	395,472
Operating Income	112,723	106,285	94,844
Other income (expense), net	3,222	(1,847)	(607)
Interest charges	21,765	22,224	16,146
Income from Continuing Operations Before Income Taxes	94,180	82,214	78,091
Income Taxes on Continuing Operations	23,538	21,114	21,123
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	70,642	61,100	56,968
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	686	(1,349)	(388)
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	170	5,402
Net Income (Loss) Attributable to Parent	$ 71,498	$ 65,153	$ 56,580
Weighted Average Common Shares Outstanding:
Basic (in shares)	16,711,579	16,398,443	16,369,616
Diluted (in shares)	16,770,735	16,448,486	16,419,870
Basic Earnings Per Share of Common Stock:
Income (Loss) from Continuing Operations, Per Basic Share	$ 4.23	$ 3.73	$ 3.48
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Basic Share	0.05	0.24	(0.02)
Basic (in usd per share)	4.28	3.97	3.46
Earnings Per Share, Diluted [Abstract]
Income (Loss) from Continuing Operations, Per Diluted Share	4.21	3.72	3.47
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Diluted Share	0.05	0.24
Diluted (in usd per share)	$ 4.26	$ 3.96	$ 3.45