Revenue (Details-1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Total Operating Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	$ 538,633	$ 568,855	$ 559,768
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	393,692	408,285	400,882
Electric [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	146,431	140,006	138,566
Electric [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	198,043	213,265	204,683
Electric [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	11,514	12,772	13,878
Electric [Member] | Other-retail/municipal [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	32,915	35,174	34,023
Electric [Member] | Total Retail [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	388,903	401,217	391,150
Electric [Member] | Sales To The Market [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	4,015	5,664	7,438
Electric [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	774	1,404	2,294
Gas [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	144,261	159,875	157,767
Gas [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	88,765	95,146	94,017
Gas [Member] | Commercial/Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	49,682	59,051	59,060
Gas [Member] | Total Retail [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	138,447	154,197	153,077
Gas [Member] | Gas Transportation [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	5,713	5,293	4,283
Gas [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	101	385	407
Non Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	$ 680	$ 695	$ 1,119