Rate Matters and Regulation	9 Months Ended
Sep. 30, 2018
Regulated Operations [Abstract]
Rate Matters and Regulation	5. RATE MATTERS AND REGULATION KCC Proceedings Westar Energy 2018 Transmission Delivery Charge In March 2018, the KCC issued an order adjusting Westar Energy's retail prices to include updated transmission costs as reflected in the FERC transmission formula rate (TFR). The new prices were effective in April 2018 and are expected to increase Westar Energy's annual retail revenues by $31.5 million. In August 2018, Westar Energy filed an updated Transmission Delivery Charge (TDC) tariff with the KCC to reflect the reduction in revenue requirement that occurred as a result of the Tax Cuts and Jobs Act. The updated filing requested new prices decreasing Westar Energy's annual retail revenues by approximately $20 million. In October 2018, the KCC issued an order approving the request with the new prices effective October 30, 2018. Westar Energy 2018 Rate Case Proceedings In February 2018, Westar Energy filed an application with the KCC to request a two-step change in rates, a decrease to retail revenues of approximately $2 million in September 2018 followed by an increase in retail revenues of approximately $54 million in February 2019, with a return on equity of 9.85% and a rate-making equity ratio of 51.6%. The request reflects costs associated with the completion of the Western Plains Wind Farm, the expiration of wholesale contracts currently reflected in retail prices as offsets to retail cost of service, the expiration of production tax credits from prior wind investments and an updated depreciation study, partially offset by the impact of the Tax Cuts and Jobs Act and a portion of the savings from the merger with Great Plains Energy. In June 2018, Westar Energy, the KCC staff and several other intervenors in the case reached a non-unanimous stipulation and agreement to settle all outstanding issues in the case. The stipulation and agreement provides for a decrease to retail revenues of $66.0 million, before rebasing property tax expense, with a return on equity of 9.3%, a rate-making equity ratio of 51.46% and does not include a second step revenue requirement change as included in Westar Energy's initial application. The stipulation and agreement also provides for an approximately $16 million increase associated with rebasing property tax expense, an approximately $46 million increase in depreciation expense, allows for the recovery of an approximately $41 million wholesale contract that expires in 2019 through Westar Energy's fuel recovery mechanism and reflects customer benefits related to the impacts of the Tax Cuts and Jobs Act, including a one-time bill credit of approximately $50 million to be provided to customers following the conclusion of the rate case. In September 2018, the KCC issued an order approving the non-unanimous stipulation and agreement. The rates established by the order took effect on September 27, 2018. KCP&L 2018 Rate Case Proceedings In May 2018, KCP&L filed an application with the KCC to request an increase to its retail revenues of $26.2 million before rebasing property tax expense, with a return on equity of 9.85% and a rate-making equity ratio of 49.8%. The request reflects the impact of the Tax Cuts and Jobs Act and increases in infrastructure investment costs. KCP&L also requested an additional $6.7 million increase associated with rebasing property tax expense. In October 2018, KCP&L, the KCC staff and other intervenors reached a unanimous settlement agreement to settle all outstanding issues in the case. The settlement agreement provides for a decrease to retail revenues of $10.7 million before rebasing property tax expense, with a return on equity of 9.3%, a rate-making equity ratio of 49.09% and a one-time bill credit of $36.9 million for customer benefits related to the impacts of the Tax Cuts and Jobs Act. The unanimous settlement agreement is subject to the approval of the KCC. The new rates are expected to go into effect in December 2018. MPSC Proceedings KCP&L 2018 Rate Case Proceedings In January 2018, KCP&L filed an application with the MPSC to request an increase to its retail revenues of $8.9 million before rebasing fuel and purchased power expense, with a return on equity of 9.85% and a rate-making equity ratio of 50.03%. The request reflects the impact of the Tax Cuts and Jobs Act and increases in infrastructure investment costs, transmission related costs and property tax costs. KCP&L also requested an additional $7.5 million increase associated with rebasing fuel and purchased power expense. In September 2018, KCP&L, MPSC staff and other intervenors in the case reached several non-unanimous stipulations and agreements to settle all outstanding issues in the case. The stipulations and agreements provide for a decrease to retail revenues of $21.1 million and a one-time customer benefit of $38.7 million related to the impact of the Tax Cuts and Jobs Act, which will be offset against existing KCP&L regulatory assets. The final amount of the one-time customer benefit related to the impact of the Tax Cuts and Jobs Act is dependent on the effective date of new rates. In October 2018, the MPSC issued an order approving the non-unanimous stipulations and agreements. The rates established by the order are expected to take effect no later than December 2018. GMO 2018 Rate Case Proceedings In January 2018, GMO filed an application with the MPSC to request a decrease to its retail revenues of $2.4 million before rebasing fuel and purchased power expense, with a return on equity of 9.85% and a rate-making equity ratio of 54.4%. The request reflects the impact of the Tax Cuts and Jobs Act and increases in infrastructure investment costs and transmission related costs. GMO also requested a $21.7 million increase associated with rebasing fuel and purchased power expense. In September 2018, GMO, MPSC staff and other intervenors in the case reached several non-unanimous stipulations and agreements to settle all outstanding issues in the case. The stipulations and agreements provide for a decrease to retail revenues of $24.0 million and a one-time bill credit of $29.3 million for customer benefits related to the impacts of the Tax Cuts and Jobs Act. The final amount of the one-time customer bill credit related to the impact of the Tax Cuts and Jobs Act is dependent on the effective date of new rates. In October 2018, the MPSC issued an order approving the non-unanimous stipulations and agreements. The rates established by the order are expected to take effect no later than December 2018. FERC Proceedings Westar Energy's TFR, effective in January 2018, includes projected 2018 transmission capital expenditures and operating costs and was expected to increase annual transmission revenues by $25.5 million. Due to the passage of the Tax Cuts and Jobs Act, Westar Energy requested permission from FERC to retroactively reflect the reduction in the federal corporate income tax rate in its 2018 prices. In April 2018, FERC granted the request and Westar Energy has recorded a regulatory liability as of September 30, 2018 of $5.9 million related to this request. It is estimated the revised TFR will increase 2018 revenues by $2.3 million when compared to 2017. Westar Energy's TFR, effective in January 2019, includes projected 2019 transmission capital expenditures and operating costs and is expected to decrease annual transmission revenues by $11.2 million when compared to 2018.

5. RATE MATTERS AND REGULATION

KCC Proceedings

Westar Energy 2018 Transmission Delivery Charge

In March 2018, the KCC issued an order adjusting Westar Energy's retail prices to include updated transmission costs as reflected in the FERC transmission formula rate (TFR). The new prices were effective in April 2018 and are expected to increase Westar Energy's annual retail revenues by $31.5 million.

In August 2018, Westar Energy filed an updated Transmission Delivery Charge (TDC) tariff with the KCC to reflect the reduction in revenue requirement that occurred as a result of the Tax Cuts and Jobs Act. The updated filing requested new prices decreasing Westar Energy's annual retail revenues by approximately $20 million. In October 2018, the KCC issued an order approving the request with the new prices effective October 30, 2018.

Westar Energy 2018 Rate Case Proceedings

In February 2018, Westar Energy filed an application with the KCC to request a two-step change in rates, a decrease to retail revenues of approximately $2 million in September 2018 followed by an increase in retail revenues of approximately $54 million in February 2019, with a return on equity of 9.85% and a rate-making equity ratio of 51.6%. The request reflects costs associated with the completion of the Western Plains Wind Farm, the expiration of wholesale contracts currently reflected in retail prices as offsets to retail cost of service, the expiration of production tax credits from prior wind investments and an updated depreciation study, partially offset by the impact of the Tax Cuts and Jobs Act and a portion of the savings from the merger with Great Plains Energy.

In June 2018, Westar Energy, the KCC staff and several other intervenors in the case reached a non-unanimous stipulation and agreement to settle all outstanding issues in the case. The stipulation and agreement provides for a decrease to retail revenues of $66.0 million, before rebasing property tax expense, with a return on equity of 9.3%, a rate-making equity ratio of 51.46% and does not include a second step revenue requirement change as included in Westar Energy's initial application. The stipulation and agreement also provides for an approximately $16 million increase associated with rebasing property tax expense, an approximately $46 million increase in depreciation expense, allows for the recovery of an approximately $41 million wholesale contract that expires in 2019 through Westar Energy's fuel recovery mechanism and reflects customer benefits related to the impacts of the Tax Cuts and Jobs Act, including a one-time bill credit of approximately $50 million to be provided to customers following the conclusion of the rate case.

In September 2018, the KCC issued an order approving the non-unanimous stipulation and agreement. The rates established by the order took effect on September 27, 2018.

KCP&L 2018 Rate Case Proceedings

In May 2018, KCP&L filed an application with the KCC to request an increase to its retail revenues of $26.2 million before rebasing property tax expense, with a return on equity of 9.85% and a rate-making equity ratio of 49.8%. The request reflects the impact of the Tax Cuts and Jobs Act and increases in infrastructure investment costs. KCP&L also requested an additional $6.7 million increase associated with rebasing property tax expense.

In October 2018, KCP&L, the KCC staff and other intervenors reached a unanimous settlement agreement to settle all outstanding issues in the case. The settlement agreement provides for a decrease to retail revenues of $10.7 million before rebasing property tax expense, with a return on equity of 9.3%, a rate-making equity ratio of 49.09% and a one-time bill credit of $36.9 million for customer benefits related to the impacts of the Tax Cuts and Jobs Act.

The unanimous settlement agreement is subject to the approval of the KCC. The new rates are expected to go into effect in December 2018.

MPSC Proceedings

KCP&L 2018 Rate Case Proceedings

In January 2018, KCP&L filed an application with the MPSC to request an increase to its retail revenues of $8.9 million before rebasing fuel and purchased power expense, with a return on equity of 9.85% and a rate-making equity ratio of 50.03%. The request reflects the impact of the Tax Cuts and Jobs Act and increases in infrastructure investment costs, transmission related costs and property tax costs. KCP&L also requested an additional $7.5 million increase associated with rebasing fuel and purchased power expense.

In September 2018, KCP&L, MPSC staff and other intervenors in the case reached several non-unanimous stipulations and agreements to settle all outstanding issues in the case. The stipulations and agreements provide for a decrease to retail revenues of $21.1 million and a one-time customer benefit of $38.7 million related to the impact of the Tax Cuts and Jobs Act, which will be offset against existing KCP&L regulatory assets. The final amount of the one-time customer benefit related to the impact of the Tax Cuts and Jobs Act is dependent on the effective date of new rates.

In October 2018, the MPSC issued an order approving the non-unanimous stipulations and agreements. The rates established by the order are expected to take effect no later than December 2018.

GMO 2018 Rate Case Proceedings

In January 2018, GMO filed an application with the MPSC to request a decrease to its retail revenues of $2.4 million before rebasing fuel and purchased power expense, with a return on equity of 9.85% and a rate-making equity ratio of 54.4%. The request reflects the impact of the Tax Cuts and Jobs Act and increases in infrastructure investment costs and transmission related costs. GMO also requested a $21.7 million increase associated with rebasing fuel and purchased power expense.

In September 2018, GMO, MPSC staff and other intervenors in the case reached several non-unanimous stipulations and agreements to settle all outstanding issues in the case. The stipulations and agreements provide for a decrease to retail revenues of $24.0 million and a one-time bill credit of $29.3 million for customer benefits related to the impacts of the Tax Cuts and Jobs Act. The final amount of the one-time customer bill credit related to the impact of the Tax Cuts and Jobs Act is dependent on the effective date of new rates.

In October 2018, the MPSC issued an order approving the non-unanimous stipulations and agreements. The rates established by the order are expected to take effect no later than December 2018.

FERC Proceedings

Westar Energy's TFR, effective in January 2018, includes projected 2018 transmission capital expenditures and operating costs and was expected to increase annual transmission revenues by $25.5 million. Due to the passage of the Tax Cuts and Jobs Act, Westar Energy requested permission from FERC to retroactively reflect the reduction in the federal corporate income tax rate in its 2018 prices. In April 2018, FERC granted the request and Westar Energy has recorded a regulatory liability as of September 30, 2018 of $5.9 million related to this request. It is estimated the revised TFR will increase 2018 revenues by $2.3 million when compared to 2017.

Westar Energy's TFR, effective in January 2019, includes projected 2019 transmission capital expenditures and operating costs and is expected to decrease annual transmission revenues by $11.2 million when compared to 2018.