Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Current Assets:
Cash and cash equivalents	$ 68,813		$ 46,357
Accounts receivable, less reserves	44,890	[1]	41,386	[2]
Other accounts receivables, less reserves	5,352	[3]	6,746	[4]
Unbilled revenues	31,982		28,262
Materials and supplies, at average cost	16,662		16,997
Fossil fuel	5,206		6,367
Stored natural gas, at average cost	13,988		14,980
Prepaid taxes	19,106		19,520
Regulatory assets - current	6,377		10,327
Deferred income taxes	0		23,483
Other current assets	8,225		8,512
Total Current Assets	220,601		222,937
Other long-term receivables	2,193		1,102
Regulatory assets	107,166		218,853
Pension and other postretirement benefits	15,071		0
Other deferred assets and other	5,853		5,973
Property, Plant, and Equipment:
Property, plant, and equipment, net	1,018,809		975,053
Construction work in progress	141,415		98,411
Total Property, Plant, and Equipment	1,160,224		1,073,464
Investments	67,952		64,595
Total Assets	1,579,060		1,586,924
Current Liabilities:
Long-term debt due within one year	4,102		3,013
Accounts payable	43,684		43,518
Accrued interest and taxes	5,661		4,296
Accrued payroll related items	10,731		10,063
Deferred income taxes	1,711		0
Regulatory liabilities - current	13,538		0
Derivative liabilities	7,750		9,270
Other current liabilities	9,489		5,637
Total Current Liabilities	96,666		75,797
Other Credits:
Deferred income taxes	284,791		270,410
Investment tax credit - deferred	1,413		1,520
Regulatory liabilities	19,792		24,538
Accrued pension and other postretirement benefits	49,184		162,835
Derivative liabilities	57,930		63,320
Other deferred liabilities and other	52,360		50,584
Total Other Credits	465,470		573,207
Common shareholders' equity:
Common stock	34,668	[5]	34,668	[5]
Additional paid-in capital	316,268		316,268
Retained earnings	266,197		228,399
Accumulated other comprehensive income, net of tax	377		94
Total Common Shareholders' Equity	617,510		579,429
Long-term debt	399,414		358,491
Total Capitalization	1,016,924		937,920
Commitments and contingencies (see Footnote 18)	0		0
Total Liabilities and Capitalization	1,579,060		1,586,924
MGE [Member]
Current Assets:
Cash and cash equivalents	14,808		6,350
Accounts receivable, less reserves	44,890	[1]	41,386	[2]
Affiliate receivables	534		634
Other accounts receivables, less reserves	5,274	[3]	6,732	[4]
Unbilled revenues	31,982		28,262
Materials and supplies, at average cost	16,662		16,997
Fossil fuel	5,206		6,367
Stored natural gas, at average cost	13,988		14,980
Prepaid taxes	23,934		23,561
Regulatory assets - current	6,377		10,327
Deferred income taxes	0		23,305
Other current assets	8,197		8,488
Total Current Assets	171,852		187,389
Affiliate receivable long-term	5,825		6,354
Regulatory assets	107,166		218,853
Pension and other postretirement benefits	15,071		0
Other deferred assets and other	6,138		6,540
Property, Plant, and Equipment:
Property, plant, and equipment, net	1,017,877		974,549
Construction work in progress	141,415		98,411
Total Property, Plant, and Equipment	1,159,292		1,072,960
Investments	65,299		61,555
Total Assets	1,530,643		1,553,651
Current Liabilities:
Long-term debt due within one year	4,102		3,013
Accounts payable	43,684		43,517
Affiliate payables	34		767
Accrued interest and taxes	6,040		4,248
Accrued payroll related items	10,731		10,063
Deferred income taxes	2,723		0
Regulatory liabilities - current	13,538		0
Derivative liabilities	7,750		9,270
Other current liabilities	6,412		4,491
Total Current Liabilities	95,014		75,369
Other Credits:
Deferred income taxes	279,085		266,231
Investment tax credit - deferred	1,413		1,520
Regulatory liabilities	19,792		24,538
Accrued pension and other postretirement benefits	49,184		162,835
Derivative liabilities	57,930		63,320
Other deferred liabilities and other	52,357		50,581
Total Other Credits	459,761		569,025
Common shareholders' equity:
Common stock	17,348	[6]	17,348	[6]
Additional paid-in capital	192,417		192,417
Retained earnings	247,534		223,527
Accumulated other comprehensive income, net of tax	192		4
Total Common Shareholders' Equity	457,491		433,296
Noncontrolling interest	118,963		117,470
Total Equity	576,454		550,766
Long-term debt	399,414		358,491
Total Capitalization	975,868		909,257
Commitments and contingencies (see Footnote 18)	0		0
Total Liabilities and Capitalization	$ 1,530,643		$ 1,553,651

[1] less reserves of $4,219

[2] less reserves of $3,885

[3] less reserves of $750

[4] less reserves of $931

[5] $1 par value - 50,000 shares authorized; 34,668 shares issued and outstanding

[6] $1 par value - 50,000 shares authorized; 17,348 shares outstanding