Revenue Recognition (Details)	3 Months Ended
	Mar. 31, 2022 USD ($) service member	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)
Revenue Recognition
Number of electric distribution cooperative members | member	38
Number of services provided | service	2
Member energy requirements supplied	57.00%	55.00%
Margins for interest ratio	1.10
Targeted margins for interest ratio	1.14
Refund liability	$ 0	$ 0
Operating revenues	420,442,000	376,331,000
Members
Revenue Recognition
Operating revenues	417,449,000	376,272,000
Receivables from contracts	137,121,000		$ 143,715,000
Non-Members
Revenue Recognition
Operating revenues	2,993,000	59,000
Receivables from contracts	2,095,000		$ 302,000
Capacity revenues | Members
Revenue Recognition
Operating revenues	243,291,000	255,824,000
Energy revenues | Members
Revenue Recognition
Operating revenues	174,158,000	120,448,000
Energy revenues | Non-Members
Revenue Recognition
Operating revenues	$ 2,993,000	$ 59,000