Madison Gas and Electric Company Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Items not affecting cash:
Depreciation and amortization	$ 53,077	$ 44,646	$ 44,225
Deferred income taxes	(4,082)	22,421	21,927
Provision for doubtful receivables	1,016	1,196	596
Employee benefit plan cost	831	295	3,333
Equity earnings in MGE Transco	(10,125)	(8,428)	(7,728)
Gain on sale of property	(1,547)	0	0
Other items	748	1,426	721
Changes in working capital items:
Trade and other receivables (change)	(4,502)	(3,594)	4,508
Inventories (change)	(2,568)	7,273	(2,646)
Unbilled revenues (change)	(1,554)	(4,838)	6,254
Prepaid taxes (change)	101	8,616	3,658
Other current assets (change)	(1,275)	700	978
Accounts payable (change)	(5,290)	9,881	(3,499)
Other current liabilities (change)	3,948	(1,738)	(597)
Dividend income from MGE Transco	8,803	5,854	6,645
Cash contributions to pension and other postretirement plans	(11,304)	(14,452)	(13,676)
Other noncurrent items, net	9,108	2,695	5,143
Cash Provided by Operating Activities	132,991	147,513	141,185
Investing Activities:
Capital expenditures	(108,131)	(83,659)	(72,030)
Capital contributions to investments	(11,081)	(2,958)	(1,053)
Proceeds from sale of property	2,819	0	0
Other	32	(209)	(230)
Cash Used for Investing Activities	(116,361)	(86,826)	(73,313)
Financing Activities:
Repayment of long-term debt	(34,358)	(4,267)	(4,182)
Issuance of long-term debt	70,000	0	0
Proceeds from (repayments of) short-term debt	4,000	0	(7,000)
Other	(597)	(70)	(1,018)
Cash Used for Financing Activities	(4,637)	(46,112)	(52,243)
Change in cash and cash equivalents:	11,993	14,575	15,629
Cash and cash equivalents at beginning of period	95,959	81,384	65,755
Cash and cash equivalents at end of period	107,952	95,959	81,384
Supplemental disclosures of cash flow information:
Interest paid	19,176	19,415	19,636
Income taxes paid	27,149	21,831	23,800
Income taxes received	0	(10,000)	(10,130)
Significant noncash investing activities:
Accrued capital expenditures	16,602	16,376	3,963
MGE [Member]
Operating Activities:
Net Income	93,072	74,592	71,465
Items not affecting cash:
Depreciation and amortization	53,077	44,622	44,178
Deferred income taxes	(7,760)	20,876	18,843
Provision for doubtful receivables	1,016	1,196	596
Employee benefit plan cost	831	295	3,333
Equity earnings in MGE Transco	0	(6,366)	(7,728)
Gain on sale of property	(1,547)	0	0
Other items	1,515	1,954	1,223
Changes in working capital items:
Trade and other receivables (change)	(4,113)	(3,583)	11,079
Inventories (change)	(2,568)	7,273	(2,647)
Unbilled revenues (change)	(1,554)	(4,838)	6,254
Prepaid taxes (change)	725	8,481	4,824
Other current assets (change)	(1,277)	699	976
Accounts payable (change)	(5,312)	9,941	(3,587)
Accrued interest and taxes (change)	118	419	(18)
Other current liabilities (change)	1,941	(2,137)	1,885
Dividend income from MGE Transco	0	5,032	6,645
Cash contributions to pension and other postretirement plans	(11,304)	(14,452)	(13,677)
Other noncurrent items, net	8,878	2,497	4,816
Cash Provided by Operating Activities	125,738	146,501	148,460
Investing Activities:
Capital expenditures	(108,131)	(83,659)	(72,030)
Capital contributions to investments	0	(1,598)	(710)
Proceeds from sale of property	1,721	0	0
Other	(248)	(391)	(180)
Cash Used for Investing Activities	(106,658)	(85,648)	(72,920)
Financing Activities:
Cash dividends paid to parent by MGE	(45,000)	(50,000)	(30,000)
Distributions to parent from noncontrolling interest	(18,000)	(24,113)	(14,708)
Equity contribution received by noncontrolling interest	0	1,598	3,230
Repayment of long-term debt	(34,358)	(4,267)	(4,182)
Issuance of long-term debt	70,000	0	0
Proceeds from (repayments of) short-term debt	4,000	0	(7,000)
Other	(539)	(63)	(682)
Cash Used for Financing Activities	(23,897)	(76,845)	(53,342)
Change in cash and cash equivalents:	(4,817)	(15,992)	22,198
Cash and cash equivalents at beginning of period	10,768	26,760	4,562
Cash and cash equivalents at end of period	5,951	10,768	26,760
Supplemental disclosures of cash flow information:
Interest paid	19,176	19,415	19,636
Income taxes paid	1	29	29
Significant noncash investing activities:
Accrued capital expenditures	16,602	16,376	3,963
Dividend in kind to parent	$ 0	$ 15,822	$ 0