Regulatory Matters	9 Months Ended
Sep. 30, 2013
Regulated Operations [Abstract]
Regulatory Matters	17. REGULATORY MATTERS KCP&L Missouri Rate Case Proceedings On January 9, 2013, the MPSC issued an order for KCP&L authorizing an increase in annual revenues of $67.4 million effective January 26, 2013. Appeals of the January 9, 2013, MPSC order were filed in February 2013 with the Missouri Court of Appeals, Western District (Court of Appeals) by KCP&L and the Missouri Energy Consumers Group (MECG) regarding various issues. On May 16, 2013, the Court of Appeals granted KCP&L's request to withdraw its appeal. On January 23, 2013, the MPSC issued an order granting expedited treatment and approving compliance tariffs implementing rates reflecting the increase in annual revenues authorized in the January 9, 2013, order. On February 6, 2013, the Office of Public Counsel (OPC) filed a Writ of Mandamus asking the Court of Appeals to direct the MPSC to vacate and rescind its January 23, 2013, order approving the tariffs because the order did not provide the OPC with a reasonable amount of time to review and/or file a motion for rehearing on the tariffs. On September 10, 2013, the Court of Appeals granted the Writ of Mandamus. On October 9, 2013, the MPSC issued an order vacating its January 23, 2013, order approving the expedited tariffs, effective November 8, 2013. The MECG also appealed the January 23, 2013, order in February 2013. The Court of Appeals has not yet issued its decision on the MECG appeal. The rates established by the January 9, 2013, MPSC order are effective unless and until modified by the MPSC or stayed by a court. GMO Missouri Rate Case Proceedings On January 9, 2013, the MPSC issued an order for GMO authorizing an increase in annual revenues of $26.2 million for its Missouri Public Service division and $21.7 million for its St. Joseph Light & Power (L&P) division effective January 26, 2013. Appeals of the January 9, 2013, MPSC order were filed in February 2013 with the Court of Appeals by GMO and MECG regarding various issues. On January 23, 2013, the MPSC issued an order granting expedited treatment and approving compliance tariffs implementing rates reflecting the increase in annual revenues authorized in the January 9, 2013, order. On February 6, 2013, the OPC filed a Writ of Mandamus asking the Court of Appeals to direct the MPSC to vacate and rescind its January 23, 2013, order approving the tariffs because the order did not provide the OPC with a reasonable amount of time to review and/or file a motion for rehearing on the tariffs. On September 10, 2013, the Court of Appeals granted the Writ of Mandamus. On October 9, 2013, the MPSC issued an order vacating its January 23, 2013, order approving the expedited tariffs, effective November 8, 2013. The MECG also appealed the January 23, 2013, order in February 2013. The Court of Appeals has not yet issued its decision on the appeals. The rates established by the January 9, 2013, MPSC order are effective unless and until modified by the MPSC or stayed by a court.

17. REGULATORY MATTERS

KCP&L Missouri Rate Case Proceedings

On January 9, 2013, the MPSC issued an order for KCP&L authorizing an increase in annual revenues of $67.4 million effective January 26, 2013. Appeals of the January 9, 2013, MPSC order were filed in February 2013 with the Missouri Court of Appeals, Western District (Court of Appeals) by KCP&L and the Missouri Energy Consumers Group (MECG) regarding various issues. On May 16, 2013, the Court of Appeals granted KCP&L's request to withdraw its appeal.

On January 23, 2013, the MPSC issued an order granting expedited treatment and approving compliance tariffs implementing rates reflecting the increase in annual revenues authorized in the January 9, 2013, order. On February 6, 2013, the Office of Public Counsel (OPC) filed a Writ of Mandamus asking the Court of Appeals to direct the MPSC to vacate and rescind its January 23, 2013, order approving the tariffs because the order did not provide the OPC with a reasonable amount of time to review and/or file a motion for rehearing on the tariffs. On September 10, 2013, the Court of Appeals granted the Writ of Mandamus. On October 9, 2013, the MPSC issued an order vacating its January 23, 2013, order approving the expedited tariffs, effective November 8, 2013.

The MECG also appealed the January 23, 2013, order in February 2013. The Court of Appeals has not yet issued its decision on the MECG appeal.

The rates established by the January 9, 2013, MPSC order are effective unless and until modified by the MPSC or stayed by a court.

GMO Missouri Rate Case Proceedings

On January 9, 2013, the MPSC issued an order for GMO authorizing an increase in annual revenues of $26.2 million for its Missouri Public Service division and $21.7 million for its St. Joseph Light & Power (L&P) division effective January 26, 2013. Appeals of the January 9, 2013, MPSC order were filed in February 2013 with the Court of Appeals by GMO and MECG regarding various issues.

On January 23, 2013, the MPSC issued an order granting expedited treatment and approving compliance tariffs implementing rates reflecting the increase in annual revenues authorized in the January 9, 2013, order. On February 6, 2013, the OPC filed a Writ of Mandamus asking the Court of Appeals to direct the MPSC to vacate and rescind its January 23, 2013, order approving the tariffs because the order did not provide the OPC with a reasonable amount of time to review and/or file a motion for rehearing on the tariffs. On September 10, 2013, the Court of Appeals granted the Writ of Mandamus. On October 9, 2013, the MPSC issued an order vacating its January 23, 2013, order approving the expedited tariffs, effective November 8, 2013.

The MECG also appealed the January 23, 2013, order in February 2013. The Court of Appeals has not yet issued its decision on the appeals.

The rates established by the January 9, 2013, MPSC order are effective unless and until modified by the MPSC or stayed by a court.