Revenue Recognition - Additional Information (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) member service	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Revenue Recognition
Number of electric distribution cooperative members | member			38
Number of services provided | service			2
Member energy requirements supplied	68.00%	65.00%	62.00%	61.00%
Margins for interest ratio			1.10
Targeted margins for interest ratio			1.14
Refund liability	$ 9,022,000	$ 16,500,000	$ 9,022,000	$ 16,500,000
Operating revenues	704,265,000	460,822,000	1,657,835,000	1,195,280,000
Members
Revenue Recognition
Operating revenues	627,130,000	437,240,000	1,523,361,000	1,171,433,000
Receivables from contracts	188,951,000		188,951,000		$ 143,715,000
Non-Members
Revenue Recognition
Operating revenues	77,135,000	23,582,000	134,474,000	23,847,000
Receivables from contracts	18,534,000		18,534,000		$ 302,000
Capacity revenues | Members
Revenue Recognition
Operating revenues	243,860,000	228,048,000	728,992,000	716,303,000
Energy revenues | Members
Revenue Recognition
Operating revenues	383,270,000	209,192,000	794,369,000	455,130,000
Energy revenues | Non-Members
Revenue Recognition
Operating revenues	$ 77,135,000	$ 23,582,000	$ 134,474,000	$ 23,847,000