Commitments and Contingencies (Details-1) $ in Thousands	Dec. 31, 2017 USD ($) Turbines MW
Purchase Obligation, Fiscal Year Maturity [Abstract]
Purchase obligation due in next twelve months	$ 128,064
Purchase obligation due in second year	69,565
Purchase obligation due in third year	60,348
Purchase obligation due in fourth year	55,284
Purchase obligation due in fifth year	42,006
Purchase obligation due thereafter	119,619
Coal [Member]
Purchase Obligation, Fiscal Year Maturity [Abstract]
Purchase obligation due in next twelve months	22,677	[1]
Purchase obligation due in second year	14,920	[1]
Purchase obligation due in third year	5,399	[1]
Purchase obligation due in fourth year	0	[1]
Purchase obligation due in fifth year	0	[1]
Purchase obligation due thereafter	0	[1]
Natural Gas, Transportation and Storage [Member]
Purchase Obligation, Fiscal Year Maturity [Abstract]
Purchase obligation due in next twelve months	20,981	[2]
Purchase obligation due in second year	20,830	[2]
Purchase obligation due in third year	20,830	[2]
Purchase obligation due in fourth year	20,830	[2]
Purchase obligation due in fifth year	20,830	[2]
Purchase obligation due thereafter	74,141	[2]
Natural Gas, Supply [Member]
Purchase Obligation, Fiscal Year Maturity [Abstract]
Purchase obligation due in next twelve months	13,709	[3]
Purchase obligation due in second year	0	[3]
Purchase obligation due in third year	0	[3]
Purchase obligation due in fourth year	0	[3]
Purchase obligation due in fifth year	0	[3]
Purchase obligation due thereafter	0	[3]
Purchase Power [Member]
Purchase Obligation, Fiscal Year Maturity [Abstract]
Purchase obligation due in next twelve months	44,350	[4]
Purchase obligation due in second year	32,444	[4]
Purchase obligation due in third year	31,479	[4]
Purchase obligation due in fourth year	32,120	[4]
Purchase obligation due in fifth year	18,887	[4]
Purchase obligation due thereafter	$ 44,641	[4]
Purchase Power Agreement, Osceola Windpower II, LLC [Member]
Purchase Power Agreement [Abstract]
Long-term purchase commitment, minimum power required (in MW) | MW	50
Saratoga Wind [Member]
Purchase Obligation, Fiscal Year Maturity [Abstract]
Purchase obligation due in next twelve months	$ 18,903	[5]
Purchase obligation due in second year	0	[5]
Purchase obligation due in third year	1,399	[5]
Purchase obligation due in fourth year	1,399	[5]
Purchase obligation due in fifth year	1,399	[5]
Purchase obligation due thereafter	$ 0	[5]
Saratoga Wind Project [Member]
Saratoga Wind
Saratoga Capacity (MW) | MW	66
Saratoga Turbines | Turbines	33
Projected Saratoga Wind Project Costs	$ 108,000
Other [Member]
Purchase Obligation, Fiscal Year Maturity [Abstract]
Purchase obligation due in next twelve months	7,444
Purchase obligation due in second year	1,371
Purchase obligation due in third year	1,241
Purchase obligation due in fourth year	935
Purchase obligation due in fifth year	890
Purchase obligation due thereafter	$ 837

[1] Total coal commitments for the Columbia and Elm Road Units , including transportation . Fuel procurement for MGE's jointly owned Columbia and Elm Road Units is handled by WPL and WEPCO, respectively, who are the operators of those facilities .

[2] MGE's natural gas transportation and storage contracts require fixed monthly payments for firm supply pipeline transportation and storage capacity. The pricing components of the fixed monthly payments for the transportation and storage contracts are established by FERC but may be subject to change.

[3] These commitments include market-based pricing.

[4] MGE has several purchase power agreements to help meet future electric supply requirements. Management expects to recover these costs in future customer rates. In October 2008, MGE entered into a purchase power agreement to help meet future electric supply requirements. Under this agreement, MGE has agreed to purchase 50  M W of wind power from Osceola Windpower II, LLC, which is located i n Iowa. This facility became operational in October 2008. MGE does not have any capacity payment commitments under this agreement. However, MGE is obligated to purchase its ratable share of the energy produced by the project. MGE's commitment related to it s ratable share of energy produced by the project has been estimated and is included in the above numbers.

[5] The Saratoga Wind Farm is a planned 66 MW wind farm, consisting of 33 turbines, located near Saratoga, Iowa. The project was approved by the PSCW in December 2017, and construction is expected to begin in early 2018, with an estimated capital cost of $ 108 million.