Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Revenues
Regulated Energy	$ 343,006	$ 345,281	$ 326,310
Unregulated Energy	154,150	161,904	140,076
Other	(17,552)	(16,869)	(16,740)
Total operating revenues	479,604	490,316	449,646
Operating Expenses
Regulated Energy cost of sales	102,803	121,828	118,769
Unregulated Energy and other cost of sales	51,697	68,342	53,420
Operations	137,844	132,523	121,949
Cost, Maintenance	15,679	14,387	12,701
Gain from a settlement	(130)	(130)	(130)
Depreciation and amortization	45,423	40,220	36,386
Other taxes	20,001	18,303	16,821
Total operating expenses	373,317	395,473	359,916
Operating Income	106,287	94,843	89,730
Other expense, net	(1,830)	(603)	(2,204)
Interest charges	22,224	16,146	12,530
Income from Continuing Operations Before Income Taxes	82,233	78,094	74,996
Income Taxes on Continuing Operations	21,091	21,232	14,670
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	61,142	56,862	60,326
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	(1,391)	(282)	(2,202)
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	5,402
Net Income (Loss) Attributable to Parent	$ 65,153	$ 56,580	$ 58,124
Weighted Average Common Shares Outstanding:
Basic (in shares)	16,398,443	16,369,616	16,336,789
Diluted (in shares)	16,448,486	16,419,870	16,383,352
Basic Earnings Per Share of Common Stock:
Income (Loss) from Continuing Operations, Per Basic Share	$ 3.73	$ 3.48	$ 3.69
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Basic Share	0.24	(0.02)	(0.13)
Basic (in usd per share)	3.97	3.46	3.56
Earnings Per Share, Diluted [Abstract]
Income (Loss) from Continuing Operations, Per Diluted Share	3.72	3.47	3.68
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Diluted Share	0.24	(0.02)
Diluted (in usd per share)	$ 3.96	$ 3.45	$ 3.55