Regulatory matters and revenues subject to refund	6 Months Ended
Jun. 30, 2012
Regulatory matters and revenues subject to refund [Abstract]
Regulatory matters and revenues subject to refund	Regulatory matters and revenues subject to refund On May 20, 2011, Montana-Dakota filed an application with the NDPSC requesting advance determination of prudence that the addition of the air quality control system at the Big Stone Station, to comply with the Clean Air Act and the South Dakota Regional Haze Implementation Plan, is reasonable and prudent. A hearing was held on November 29, 2011. On May 9, 2012, the NDPSC issued an order approving the advance determination of prudence. On July 7, 2011, Montana-Dakota filed for an advance determination of prudence with the NDPSC on the construction of an 88-MW simple cycle natural gas turbine and associated facilities projected to be in service in 2015. The turbine will be located on company-owned property that is adjacent to Montana-Dakota's Heskett Generating Station near Mandan, North Dakota, and would be used to meet the capacity requirements of Montana-Dakota's integrated electric system service customers. The capacity will be a partial replacement for third party contract capacity expiring in 2015. Project cost is estimated to be $85.6 million. On April 11, 2012, the NDPSC issued an order approving the advance determination of prudence and issued a Certificate of Public Convenience and Necessity. On November 15, 2011, the MNPUC issued a Notice of Investigation; Opportunity to Respond and Comment to investigate whether Great Plains' rates are unreasonable and whether Great Plains should be ordered to initiate a general rate proceeding as Great Plains has earned in excess of its authorized return and the excess earnings are likely to continue into the future. On December 2, 2011, Great Plains responded to the MNPUC's Notice. On January 30, 2012, the MNPUC issued an order that found that the reasonableness of Great Plains' rates had not been resolved to the MNPUC's satisfaction and required Great Plains to initiate a rate proceeding within 180 days of the order, unless resolved through settlement. On March 30, 2012, Great Plains and the MNDOC filed a settlement agreement with the MNPUC, in which Great Plains agreed to reduce its rates by $250,000 annually. The MNPUC approved the settlement agreement on April 26, 2012, with the revenue reduction implemented effective with service rendered on and after June 1, 2012.

Regulatory matters and revenues subject to refund

On May 20, 2011, Montana-Dakota filed an application with the NDPSC requesting advance determination of prudence that the addition of the air quality control system at the Big Stone Station, to comply with the Clean Air Act and the South Dakota Regional Haze Implementation Plan, is reasonable and prudent. A hearing was held on November 29, 2011. On May 9, 2012, the NDPSC issued an order approving the advance determination of prudence.

On July 7, 2011, Montana-Dakota filed for an advance determination of prudence with the NDPSC on the construction of an 88-MW simple cycle natural gas turbine and associated facilities projected to be in service in 2015. The turbine will be located on company-owned property that is adjacent to Montana-Dakota's Heskett Generating Station near Mandan, North Dakota, and would be used to meet the capacity requirements of Montana-Dakota's integrated electric system service customers. The capacity will be a partial replacement for third party contract capacity expiring in 2015. Project cost is estimated to be $85.6 million. On April 11, 2012, the NDPSC issued an order approving the advance determination of prudence and issued a Certificate of Public Convenience and Necessity.

On November 15, 2011, the MNPUC issued a Notice of Investigation; Opportunity to Respond and Comment to investigate whether Great Plains' rates are unreasonable and whether Great Plains should be ordered to initiate a general rate proceeding as Great Plains has earned in excess of its authorized return and the excess earnings are likely to continue into the future. On December 2, 2011, Great Plains responded to the MNPUC's Notice. On January 30, 2012, the MNPUC issued an order that found that the reasonableness of Great Plains' rates had not been resolved to the MNPUC's satisfaction and required Great Plains to initiate a rate proceeding within 180 days of the order, unless resolved through settlement. On March 30, 2012, Great Plains and the MNDOC filed a settlement agreement with the MNPUC, in which Great Plains agreed to reduce its rates by $250,000 annually. The MNPUC approved the settlement agreement on April 26, 2012, with the revenue reduction implemented effective with service rendered on and after June 1, 2012.