Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Activities:
Net Income	$ 105,761	$ 92,418	$ 86,874
Items not affecting cash:
Depreciation and amortization	76,983	74,188	71,562
Deferred income taxes	4,837	10,363	7,212
Provision for doubtful receivables	1,550	1,415	1,615
Employee benefit plan (credit) cost	(2,203)	(3,716)	(3,813)
Equity earnings in investments	(9,270)	(10,221)	(9,889)
Other items	120	(2,750)	163
Changes in working capital items:
Accounts receivable and unbilled revenues (change)	(24,651)	(5,451)	1,060
Inventories (change)	(6,342)	(842)	(3,420)
Prepaid taxes (change)	(5,035)	1,713	(677)
Other current assets (change)	(192)	(1,057)	29
Accounts payable (change)	2,729	14,353	(7,432)
Other current liabilities (change)	(6,734)	(5,635)	(10,264)
Dividends from investment	7,832	8,998	7,347
Cash contributions to pension and other postretirement plans	(6,935)	(6,296)	(5,714)
Other noncurrent items, net	(923)	4,963	(4,178)
Cash Provided by Operating Activities	137,527	172,443	130,475
Investing Activities:
Capital expenditures	(153,169)	(203,139)	(164,036)
Capital contributions to investments	(4,027)	(5,601)	(7,813)
Other	221	(1,672)	(508)
Cash Used for Investing Activities	(156,975)	(210,412)	(172,357)
Financing Activities:
Issuance of common stock, net	0	79,635	0
Cash dividends paid on common stock	(54,788)	(51,729)	(47,842)
Repayment of long-term debt	(4,771)	(38,959)	(4,553)
Issuance of long-term debt	100,000	19,300	50,000
Proceeds from (Repayments of) short-term debt	(47,000)	52,500	(13,000)
Other	(2,197)	(1,553)	(1,838)
Cash Provided by (Used for) Financing Activities	(8,756)	59,194	(17,233)
Change in cash, cash equivalents, and restricted cash:	(28,204)	21,225	(59,115)
Cash, cash equivalents, and restricted cash at beginning of period	47,039	25,814	84,929
Cash, cash equivalents, and restricted cash at end of period	18,835	47,039	25,814
Supplemental disclosures of cash flow information:
Interest paid	23,502	23,898	23,171
Income taxes paid	4,000	8,127	14,617
Income taxes received	0	0	(255)
Significant noncash investing activities:
Accrued capital expenditures	14,414	5,719	26,697
MGE [Member]
Operating Activities:
Net Income	100,782	85,523	80,779
Items not affecting cash:
Depreciation and amortization	76,983	74,188	71,562
Deferred income taxes	3,654	8,543	5,286
Provision for doubtful receivables	1,550	1,415	1,615
Employee benefit plan (credit) cost	(2,203)	(3,716)	(3,813)
Other items	2,002	(1,828)	1,256
Changes in working capital items:
Accounts receivable and unbilled revenues (change)	(24,680)	(5,453)	1,060
Inventories (change)	(6,342)	(842)	(3,420)
Prepaid taxes (change)	(4,531)	616	327
Other current assets (change)	(148)	(1,157)	147
Accounts payable (change)	2,775	14,603	(7,754)
Accrued interest and taxes (change)	244	1,651	(1,565)
Other current liabilities (change)	(11,107)	(4,909)	(9,618)
Cash contributions to pension and other postretirement plans	(6,935)	(6,296)	(5,714)
Other noncurrent items, net	(1,804)	3,980	(4,278)
Cash Provided by Operating Activities	130,240	166,318	125,870
Investing Activities:
Capital expenditures	(153,169)	(203,139)	(164,036)
Other	(1,709)	(2,122)	(782)
Cash Used for Investing Activities	(154,878)	(205,261)	(164,818)
Financing Activities:
Cash dividends paid to parent by MGE	(5,000)	0	0
Distributions to parent from noncontrolling interest	(15,000)	(21,500)	(23,500)
Capital contributions from parent	0	30,000	30,500
Repayment of long-term debt	(4,771)	(38,959)	(4,553)
Issuance of long-term debt	100,000	19,300	50,000
Proceeds from (Repayments of) short-term debt	(47,000)	52,500	(13,000)
Other	(2,197)	(1,523)	(1,640)
Cash Provided by (Used for) Financing Activities	26,032	39,818	37,807
Change in cash, cash equivalents, and restricted cash:	1,394	875	(1,141)
Cash, cash equivalents, and restricted cash at beginning of period	6,404	5,529	6,670
Cash, cash equivalents, and restricted cash at end of period	7,798	6,404	5,529
Supplemental disclosures of cash flow information:
Interest paid	23,502	23,898	23,171
Income taxes paid	0	0	95
Income taxes received	0	0	(249)
Significant noncash investing activities:
Accrued capital expenditures	$ 14,414	$ 5,719	$ 26,697