Revenue (Details-1) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Total Operating Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	$ 138,198	$ 137,795	$ 427,914	$ 419,689
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	120,607	119,175	314,886	312,633
Electric [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	42,442	42,371	107,772	107,847
Electric [Member] | Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	63,466	61,638	165,481	159,264
Electric [Member] | Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	3,760	3,668	10,013	11,193
Electric [Member] | Other-retail/municipal
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	9,543	9,431	26,728	26,245
Electric [Member] | Total Retail [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	119,211	117,108	309,994	304,549
Electric [Member] | Sales To The Market [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	1,163	1,505	3,914	6,334
Electric [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	233	562	978	1,750
Gas [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	17,377	18,407	112,547	106,152
Gas [Member] | Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	11,342	11,916	67,659	64,087
Gas [Member] | Commercial/Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	4,825	5,570	40,833	38,728
Gas [Member] | Total Retail [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	16,167	17,486	108,492	102,815
Gas [Member] | Gas Transportation [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	1,126	829	3,756	3,018
Gas [Member] | Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	84	92	299	319
Non Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenues recognized from contracts with customers	$ 214	$ 213	$ 481	$ 904