Fair Value of Financial Instruments (Details-4) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance,		$ (2,892)	$ 8,959	$ (866)	$ 178
Realized and unrealized gains (losses):
Included in regulatory assets		1,768	0	(258)	0
Included in regulatory liability		0	(5,105)	0	3,675
Included in other comprehensive income		0	0	0	0
Included in earnings	[1]	(2,016)	6,609	(7,590)	13,607
Included in current assets		0	(73)	0	45
Purchases		0	108	0	11,911
Sales		0	0	0	0
Issuances		0	0	0	0
Settlements		2,016	(6,644)	7,590	(25,562)
Ending balance,		$ (1,124)	$ 3,854	$ (1,124)	$ 3,854

[1] MGE's exchange-traded derivative contracts, over-the-counter party transactions, purchased power agreement, and FTRs are subject to regulatory deferral. These derivatives are therefore marked to fair value and are offset in the financial statements with a corresponding regulatory asset or liability.