Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Current Assets:
Cash and cash equivalents	$ 65,755		$ 68,813
Accounts receivable, less reserves	41,614		44,890
Other accounts receivables, less reserves	7,610		5,352
Unbilled revenues	31,262		31,982
Materials and supplies, at average cost	17,121		16,662
Fossil fuel	8,098		5,206
Stored natural gas, at average cost	21,036		13,988
Prepaid taxes	38,910		19,106
Regulatory assets - current	8,360		6,377
Deferred income taxes	3,482		0
Other current assets	10,711		8,225
Total Current Assets	253,959		220,601
Other long-term receivables	2,181		2,193
Regulatory assets	156,823		107,166
Pension and other postretirement benefits	0		15,071
Other deferred assets and other	4,837		5,853
Property, Plant, and Equipment:
Property, plant, and equipment, net	1,189,077		1,018,809
Construction work in progress	19,029		141,415
Total Property, Plant, and Equipment	1,208,106		1,160,224
Investments	71,760		67,952
Total Assets	1,697,666		1,579,060
Current Liabilities:
Long-term debt due within one year	4,182		4,102
Short-term debt	7,000	[1]	0	[1]
Accounts payable	41,655		43,684
Accrued interest and taxes	5,086		5,661
Accrued payroll related items	11,241		10,731
Deferred income taxes	0		1,711
Regulatory liabilities - current	0		13,538
Derivative liabilities	6,901		7,750
Other current liabilities	13,931		9,489
Total Current Liabilities	89,996		96,666
Other Credits:
Deferred income taxes	342,045		284,791
Investment tax credit - deferred	1,223		1,413
Regulatory liabilities	22,715		19,792
Accrued pension and other postretirement benefits	90,201		49,184
Derivative liabilities	46,560		57,930
Other deferred liabilities and other	50,269		52,360
Total Other Credits	553,013		465,470
Common shareholders' equity:
Common stock	34,668		34,668
Additional paid-in capital	316,268		316,268
Retained earnings	308,007		266,197
Accumulated other comprehensive income, net of tax	458		377
Total Common Shareholders' Equity	659,401		617,510
Long-term debt	395,256		399,414
Total Capitalization	1,054,657		1,016,924
Commitments and contingencies (see Footnote 18)	0		0
Total Liabilities and Capitalization	1,697,666		1,579,060
MGE [Member]
Current Assets:
Cash and cash equivalents	4,562		14,808
Accounts receivable, less reserves	41,614		44,890
Affiliate receivables	7,112		534
Other accounts receivables, less reserves	7,524		5,274
Unbilled revenues	31,262		31,982
Materials and supplies, at average cost	17,121		16,662
Fossil fuel	8,098		5,206
Stored natural gas, at average cost	21,035		13,988
Prepaid taxes	39,103		23,934
Regulatory assets - current	8,360		6,377
Deferred income taxes	1,271		0
Other current assets	10,683		8,197
Total Current Assets	197,745		171,852
Affiliate receivable long-term	5,295		5,825
Regulatory assets	156,823		107,166
Pension and other postretirement benefits	0		15,071
Other deferred assets and other	4,977		6,138
Property, Plant, and Equipment:
Property, plant, and equipment, net	1,188,351		1,017,877
Construction work in progress	19,029		141,415
Total Property, Plant, and Equipment	1,207,380		1,159,292
Investments	68,402		65,299
Total Assets	1,640,622		1,530,643
Current Liabilities:
Long-term debt due within one year	4,182		4,102
Short-term debt	7,000		0
Accounts payable	41,654		43,684
Accrued interest and taxes	5,039		6,040
Accrued payroll related items	11,241		10,731
Deferred income taxes	0		2,723
Regulatory liabilities - current	0		13,538
Derivative liabilities	6,901		7,750
Other current liabilities	11,350		6,446
Total Current Liabilities	87,367		95,014
Other Credits:
Deferred income taxes	334,773		279,085
Investment tax credit - deferred	1,223		1,413
Regulatory liabilities	22,715		19,792
Accrued pension and other postretirement benefits	90,201		49,184
Derivative liabilities	46,560		57,930
Other deferred liabilities and other	50,267		52,357
Total Other Credits	545,739		459,761
Common shareholders' equity:
Common stock	17,348		17,348
Additional paid-in capital	192,417		192,417
Retained earnings	276,662		247,534
Accumulated other comprehensive income, net of tax	144		192
Total Common Shareholders' Equity	486,571		457,491
Noncontrolling interest	125,689		118,963
Total Equity	612,260		576,454
Long-term debt	395,256		399,414
Total Capitalization	1,007,516		975,868
Commitments and contingencies (see Footnote 18)	0		0
Total Liabilities and Capitalization	$ 1,640,622		$ 1,530,643

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