Consolidated Balance Sheets - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Current Assets:
Cash and cash equivalents		$ 107,952	$ 95,959
Accounts receivable, less reserves		42,299	39,887
Other accounts receivables, less reserves		9,440	8,530
Unbilled revenues		31,400	29,846
Materials and supplies, at average cost		22,614	18,561
Fuel for electric generation, at average cost		8,256	9,757
Stored natural gas, at average cost		12,923	12,819
Prepaid taxes		26,535	26,636
Regulatory assets - current		7,888	6,414
Assets held for sale		8,817	14,813
Other current assets		12,507	12,293
Total Current Assets		290,631	275,515
Other long-term receivables		4,788	5,603
Regulatory assets		142,567	158,485
Pension and other postretirement benefit asset		7,336	2,020
Other deferred assets and other		731	1,088
Property, Plant, and Equipment:
Property, plant, and equipment, net		1,283,313	1,245,269
Construction work in progress		58,044	36,790
Total Property, Plant, and Equipment		1,341,357	1,282,059
Investments		67,772	76,290
Total Assets		1,855,182	1,801,060
Current Liabilities:
Long-term debt due within one year		24,452	4,333
Short-term debt	[1]	4,000	0
Accounts payable		47,645	47,799
Accrued interest and taxes		5,602	5,495
Accrued payroll related items		12,244	11,892
Regulatory liabilities - current		5,633	6,910
Derivative liabilities		8,180	7,620
Other current liabilities		18,758	19,456
Total Current Liabilities		126,514	103,505
Other Credits:
Deferred income taxes		225,130	383,813
Investment tax credit - deferred		918	947
Regulatory liabilities		154,153	22,173
Accrued pension and other postretirement benefits		69,088	74,347
Derivative liabilities		33,990	42,970
Other deferred liabilities and other		69,041	66,426
Total Other Credits		552,320	590,676
Common shareholders' equity:
Common stock		34,668	34,668
Additional paid-in capital		316,268	316,268
Retained earnings		426,874	372,950
Accumulated other comprehensive income, net of tax		377	202
Total Common Shareholders' Equity		778,187	724,088
Long-term debt		398,161	382,791
Total Capitalization		1,176,348	1,106,879
Commitments and contingencies (see Footnote 17)
Total Liabilities and Capitalization		1,855,182	1,801,060
MGE [Member]
Current Assets:
Cash and cash equivalents		5,951	10,768
Accounts receivable, less reserves		42,299	39,887
Affiliate receivables		668	539
Other accounts receivables, less reserves		6,984	6,363
Unbilled revenues		31,400	29,846
Materials and supplies, at average cost		22,614	18,561
Fuel for electric generation, at average cost		8,256	9,757
Stored natural gas, at average cost		12,923	12,819
Prepaid taxes		25,073	25,798
Regulatory assets - current		7,888	6,414
Assets held for sale		8,817	14,813
Other current assets		12,484	12,268
Total Current Assets		185,357	187,833
Affiliate receivable long-term		3,707	4,236
Regulatory assets		142,567	158,485
Pension and other postretirement benefit asset		7,336	2,020
Other deferred assets and other		3,280	4,353
Property, Plant, and Equipment:
Property, plant, and equipment, net		1,283,341	1,244,648
Construction work in progress		58,044	36,790
Total Property, Plant, and Equipment		1,341,385	1,281,438
Investments		409	487
Total Assets		1,684,041	1,638,852
Current Liabilities:
Long-term debt due within one year		24,452	4,333
Short-term debt		4,000	0
Accounts payable		47,614	47,790
Accrued interest and taxes		5,558	5,440
Accrued payroll related items		12,244	11,892
Regulatory liabilities - current		5,633	6,910
Derivative liabilities		8,180	7,620
Other current liabilities		16,749	19,347
Total Current Liabilities		124,430	103,332
Other Credits:
Deferred income taxes		201,486	343,117
Investment tax credit - deferred		918	947
Regulatory liabilities		154,153	22,173
Accrued pension and other postretirement benefits		69,088	74,347
Derivative liabilities		33,990	42,970
Other deferred liabilities and other		69,041	66,426
Total Other Credits		528,676	549,980
Common shareholders' equity:
Common stock		17,348	17,348
Additional paid-in capital		192,417	192,417
Retained earnings		282,135	277,300
Accumulated other comprehensive income, net of tax		(28)	19
Total Common Shareholders' Equity		491,872	487,084
Noncontrolling interest		140,902	115,665
Total Equity		632,774	602,749
Long-term debt		398,161	382,791
Total Capitalization		1,030,935	985,540
Commitments and contingencies (see Footnote 17)
Total Liabilities and Capitalization		$ 1,684,041	$ 1,638,852

[1] MGE Energy short-term borrowings include MGE Energy and MGE lines of credit and MGE commercial paper.