Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation of Revenue [Line Items]
Total Operating Revenues	$ 400,040	$ 285,608	$ 774,944	$ 547,318
Operating Segments
Disaggregation of Revenue [Line Items]
Total Operating Revenues from Contracts with Customers	404,968	287,390	782,332	550,075
Operating Segments | Electric
Disaggregation of Revenue [Line Items]
Total Operating Revenues	130,949	106,155	261,365	229,855
Electric Segment - ARP Revenues	(4,928)	(1,782)	(7,388)	(2,757)
Operating Segments | Manufacturing
Disaggregation of Revenue [Line Items]
Total Operating Revenues	103,196	84,284	208,154	160,107
Operating Segments | Plastics
Disaggregation of Revenue [Line Items]
Total Operating Revenues	165,895	95,169	305,425	157,356
Operating Segments | Total Retail | Electric
Disaggregation of Revenue [Line Items]
Total Operating Revenues	113,603	88,987	227,242	194,693
Operating Segments | Retail: Residential | Electric
Disaggregation of Revenue [Line Items]
Total Operating Revenues	33,011	28,709	73,743	66,176
Operating Segments | Retail: Commercial and Industrial | Electric
Disaggregation of Revenue [Line Items]
Total Operating Revenues	78,521	58,390	149,527	124,811
Operating Segments | Retail: Other | Electric
Disaggregation of Revenue [Line Items]
Total Operating Revenues	2,071	1,888	3,972	3,706
Operating Segments | Transmission | Electric
Disaggregation of Revenue [Line Items]
Total Operating Revenues	11,697	11,840	24,254	23,785
Operating Segments | Wholesale | Electric
Disaggregation of Revenue [Line Items]
Total Operating Revenues	3,537	3,260	6,000	7,767
Operating Segments | Other | Electric
Disaggregation of Revenue [Line Items]
Total Operating Revenues	2,112	2,068	3,869	3,610
Operating Segments | Metal Parts and Tooling | Manufacturing
Disaggregation of Revenue [Line Items]
Total Operating Revenues	88,296	71,013	177,869	133,686
Operating Segments | Plastic Products and Tooling | Manufacturing
Disaggregation of Revenue [Line Items]
Total Operating Revenues	11,416	10,131	23,860	20,426
Operating Segments | Scrap Metal Sales | Manufacturing
Disaggregation of Revenue [Line Items]
Total Operating Revenues	$ 3,484	$ 3,140	$ 6,425	$ 5,995