Regulatory matters and revenues subject to refund	6 Months Ended
Jun. 30, 2013
Regulated Operations [Abstract]
Regulatory matters and revenues subject to refund	Regulatory matters and revenues subject to refund On September 26, 2012, Montana-Dakota filed an application with the MTPSC for a natural gas rate increase. Montana-Dakota requested a total increase of $3.5 million annually or approximately 5.9 percent above current rates. The requested increase includes the costs associated with the increased investment in facilities, including ongoing investment in new and replacement distribution facilities, the landfill gas production facility, a region operations building, automated meter reading and a new customer billing system. Montana-Dakota requested an interim increase, subject to refund, of $1.7 million or approximately 2.9 percent. On April 12, 2013, the MTPSC issued an interim order authorizing an interim increase of $850,000 annually to be effective with service rendered on or after April 15, 2013, subject to refund. A hearing began on August 5, 2013. On December 21, 2012, Montana-Dakota filed an application with the SDPUC for a natural gas rate increase. Montana-Dakota requested a total increase of $1.5 million annually or approximately 3.3 percent above current rates. The requested increase includes the costs associated with the increased investment in facilities, including ongoing investment in new and replacement distribution facilities, the landfill gas production facility, an operations building, automated meter reading and a new customer billing system. On June 19, 2013, Montana-Dakota filed a notice of intent to implement an interim rate increase of $1.5 million effective with service rendered on or after July 22, 2013. A hearing is scheduled to begin October 29, 2013. On February 11, 2013, Montana-Dakota filed an application with the NDPSC for approval of an environmental cost recovery rider for recovery of Montana-Dakota's share of the costs resulting from the environmental retrofit required to be installed at the Big Stone Station. The costs proposed to be recovered are associated with the ongoing construction costs for the installation of the BART air-quality control system. On February 27, 2013, the NDPSC suspended the filing pending further review. On May 31, 2013, Montana-Dakota filed revisions to its filing to reflect revised budget amounts. A hearing is scheduled to begin September 16, 2013. On June 14, 2013, Montana-Dakota filed for an advance determination of prudence with the NDPSC to add filterable particulate matter pollution control equipment at Montana-Dakota's Lewis & Clark generating station to comply with the Mercury and Air Toxics Standards rule, projected to be completed in 2016. Project cost is estimated to be $26.1 million.

Regulatory matters and revenues subject to refund

On September 26, 2012, Montana-Dakota filed an application with the MTPSC for a natural gas rate increase. Montana-Dakota requested a total increase of $3.5 million annually or approximately 5.9 percent above current rates. The requested increase includes the costs associated with the increased investment in facilities, including ongoing investment in new and replacement distribution facilities, the landfill gas production facility, a region operations building, automated meter reading and a new customer billing system. Montana-Dakota requested an interim increase, subject to refund, of $1.7 million or approximately 2.9 percent. On April 12, 2013, the MTPSC issued an interim order authorizing an interim increase of $850,000 annually to be effective with service rendered on or after April 15, 2013, subject to refund. A hearing began on August 5, 2013.

On December 21, 2012, Montana-Dakota filed an application with the SDPUC for a natural gas rate increase. Montana-Dakota requested a total increase of $1.5 million annually or approximately 3.3 percent above current rates. The requested increase includes the costs associated with the increased investment in facilities, including ongoing investment in new and replacement distribution facilities, the landfill gas production facility, an operations building, automated meter reading and a new customer billing system. On June 19, 2013, Montana-Dakota filed a notice of intent to implement an interim rate increase of $1.5 million effective with service rendered on or after July 22, 2013. A hearing is scheduled to begin October 29, 2013.

On February 11, 2013, Montana-Dakota filed an application with the NDPSC for approval of an environmental cost recovery rider for recovery of Montana-Dakota's share of the costs resulting from the environmental retrofit required to be installed at the Big Stone Station. The costs proposed to be recovered are associated with the ongoing construction costs for the installation of the BART air-quality control system. On February 27, 2013, the NDPSC suspended the filing pending further review. On May 31, 2013, Montana-Dakota filed revisions to its filing to reflect revised budget amounts. A hearing is scheduled to begin September 16, 2013.

On June 14, 2013, Montana-Dakota filed for an advance determination of prudence with the NDPSC to add filterable particulate matter pollution control equipment at Montana-Dakota's Lewis & Clark generating station to comply with the Mercury and Air Toxics Standards rule, projected to be completed in 2016. Project cost is estimated to be $26.1 million.