Rate And Regulatory Matters	6 Months Ended
Jun. 30, 2014
Public Utilities, General Disclosures [Abstract]
RATE AND REGULATORY MATTERS	RATE AND REGULATORY MATTERS Below is a summary of updates to significant regulatory proceedings and related lawsuits. See also Note 2 - Rate and Regulatory Matters under Part II, Item 8, of the Form 10-K. We are unable to predict the ultimate outcome of these matters, the timing of the final decisions of the various agencies and courts, or the impact on our results of operations, financial position, or liquidity. Missouri 2014 Electric Rate Case In July 2014, Ameren Missouri filed a request with the MoPSC seeking approval to increase its annual revenues for electric service by $264 million. The rate request seeks recovery of increased net energy costs and rebates provided for customer-installed solar generation, as well as recovery of and a return on additional electric infrastructure investments made for the benefit of Ameren Missouri’s customers. Plant additions to rate base since the last electric rate order are expected to total approximately $1.4 billion through the anticipated true-up date in this rate case and include electric infrastructure investments for upgrades to the electrostatic precipitators at the coal-fired Labadie energy center to meet more stringent environmental regulations, the replacement of the nuclear reactor vessel head at the Callaway energy center in order to ensure continued safe and dependable operations, two new substations in St. Louis, and the O’Fallon energy center, which will be Missouri’s largest investor-owned utility solar facility, among other additions. Approximately $127 million of the request relates to an increase in net energy costs above the current levels included in base rates previously authorized by the MoPSC in its December 2012 electric rate order, 95% of which, absent initiation of this general rate proceeding, would have been reflected in rate adjustments implemented under Ameren Missouri’s existing FAC. The electric rate increase request is based on a 10.4% return on equity, a capital structure composed of 51.6% common equity, an electric rate base for Ameren Missouri of $7.3 billion, and a test year ended March 31, 2014, with certain pro-forma adjustments expected through the anticipated true-up date of December 31, 2014. As a part of its filing, Ameren Missouri also requested continued use of the FAC and the regulatory tracking mechanisms for storm costs, vegetation management/infrastructure inspection costs, pension and postretirement benefits, and uncertain income tax positions that the MoPSC previously authorized in earlier electric rate orders. The MoPSC proceeding relating to the proposed electric service rate changes will take place over a period of up to 11 months and a decision by the MoPSC in such proceeding is expected by May 2015, with rates effective by June 2015. Ameren Missouri cannot predict the level of any electric service rate change the MoPSC may approve, when any rate change may go into effect or whether any rate increase that may eventually be approved will be sufficient for Ameren Missouri to recover its costs and earn a reasonable return on its investments when the increase goes into effect. Accounting Authority Order In July 2011, Ameren Missouri filed a request with the MoPSC for an accounting authority order that would allow Ameren Missouri to defer fixed costs totaling $36 million that were not previously recovered from Noranda as a result of the loss of load caused by the severe 2009 ice storm for potential recovery in a future electric rate case. In November 2013, the MoPSC issued an accounting authority order that allowed Ameren Missouri to seek recovery of these fixed costs in an electric rate case. Ameren Missouri’s July 2014 electric rate case filing requested recovery of these fixed costs over five years. In February 2014, MIEC and MoOPC filed appeals of the MoPSC’s November 2013 accounting authority order with the Missouri Court of Appeals, Western District. Ameren Missouri has not recorded any potential revenue associated with this accounting authority order. Earnings Complaint and Rate Shift Complaint Cases In February 2014, Ameren Missouri’s largest customer, Noranda, and 37 residential customers filed an earnings complaint case and a rate shift complaint case with the MoPSC. In the earnings complaint case, Noranda and the residential customers asserted that Ameren Missouri’s electric service business is earning more than the 9.8% return on common equity authorized in the MoPSC's December 2012 electric rate order. Noranda and the residential customers are currently requesting the MoPSC approve a $49 million reduction to Ameren Missouri’s annual revenue requirement. Included in Noranda’s request is a reduction of Ameren Missouri’s authorized return on common equity to 9.4%. The MoPSC staff filed testimony in this case that recommended no reduction to Ameren Missouri’s annual revenue requirement. The MoOPC and MIEC intervened in the earnings complaint case. The rate shift complaint case seeks to reduce Noranda's electric rates with an offsetting increase in electric rates for Ameren Missouri's other customers. While the rate shift proposal is revenue neutral to Ameren Missouri, Ameren Missouri does not believe that the proposed reduction to Noranda's electric rates, which would result in rates that are significantly below Ameren Missouri's cost of service, is appropriate or in the best interests of Ameren Missouri's other electric customers. While the MoPSC has no time requirement by which it must issue orders in these cases, it has adopted procedural schedules that Ameren Missouri expects would render a decision in the rate shift case during the third quarter of 2014, and in the earnings complaint case by September 26, 2014. Ameren Missouri does not believe that a reduction in electric service rates is justified and filed testimony that supports that position, which is consistent with Ameren Missouri’s July 2014 electric rate case filing. Illinois IEIMA Under the provisions of the IEIMA, Ameren Illinois’ electric delivery service rates are subject to an annual revenue requirement reconciliation to its actual costs. Throughout each year, Ameren Illinois records a regulatory asset or a regulatory liability and a corresponding increase or decrease to operating revenues for any differences between the revenue requirement in effect for customer billings for that year and its estimate of the probable increase or decrease in the revenue requirement expected to ultimately be approved by the ICC based on that year's actual costs incurred. As of June 30, 2014, Ameren Illinois had recorded a regulatory asset of $42 million and $64 million, respectively, to reflect its expected 2014 and 2013 revenue requirement reconciliation adjustments, with interest. As of June 30, 2014, Ameren Illinois had recorded a regulatory liability of $35 million to reflect its 2012 revenue requirement reconciliation adjustment, with interest, which will be refunded to customers during 2014. In September 2012 and December 2012, the ICC issued orders in Ameren Illinois’ IEIMA performance-based formula rate filings. Ameren Illinois appealed both orders to the Appellate Court of the Fourth District of Illinois. The primary issues Ameren Illinois appealed were the rate treatment of accumulated deferred income taxes and vacation obligations as well as the calculation of Ameren Illinois’ capital structure. In December 2013, the appellate court rendered its decision upholding the ICC’s September and December 2012 orders. Ameren Illinois filed an appeal to the Illinois Supreme Court in March 2014. In May 2014, the Illinois Supreme Court denied Ameren Illinois’ appeal. In December 2013, the ICC issued an order in Ameren Illinois' annual update filing, which was based on 2012 recoverable costs and expected net plant additions for 2013. The ICC order established rates for 2014. In February 2014, Ameren Illinois filed an appeal to the Appellate Court of the Fourth District of Illinois regarding the calculation of its capital structure and the rate treatment of accumulated deferred income taxes related to the transfer of former Ameren Missouri assets in Illinois to Ameren Illinois. Ameren Illinois will not pursue the calculation of its capital structure in its appeal as a result of the Illinois Supreme Court ruling discussed above in May 2014. Ameren Illinois will continue its appeal of the rate treatment of accumulated deferred income taxes. In April 2014, Ameren Illinois filed with the ICC its annual electric delivery service formula rate update to establish the revenue requirement used to set rates for 2015. Pending ICC approval, Ameren Illinois’ update filing, as revised in July 2014, will result in a $205 million increase in Ameren Illinois’ electric delivery service revenue requirement beginning in January 2015. This update reflects an increase to the annual formula rate based on 2013 actual costs and expected net plant additions for 2014, an increase to include the annual reconciliation of the revenue requirement in effect for 2013 to the actual costs incurred in that year, and an increase resulting from the conclusion of a refund to customers in 2014 for the 2012 revenue requirement reconciliation. In July 2014, the ICC staff submitted its calculation of the revenue requirement included in Ameren Illinois’ update filling. The ICC staff recommended adjustments that would result in a $202 million increase in Ameren Illinois’ electric delivery service revenue requirement. An ICC decision on this April 2014 filing is expected by December 2014. 2013 Natural Gas Delivery Service Rate Case In December 2013, the ICC issued a rate order that approved an increase in revenues for natural gas delivery service of $32 million. The revenue increase was based on a 9.1% return on equity, a capital structure composed of 51.7% common equity, and a rate base of $1.1 billion. The rate order was based on a 2014 future test year. The rate changes became effective January 1, 2014. In March 2014, Ameren Illinois filed an appeal of the allowed return on common equity included in the ICC's order and is also appealing the rate treatment of accumulated deferred income taxes related to the transfer of former Ameren Missouri assets in Illinois to Ameren Illinois with the Appellate Court of the Fourth District of Illinois. Ameren Illinois sought a 10.4% return on common equity in this rate case. Federal 2011 Wholesale Distribution Rate Case In January 2011, Ameren Illinois filed a request with FERC to increase its annual revenues for electric delivery service for its wholesale customers. These wholesale distribution revenues are treated as a deduction from Ameren Illinois’ revenue requirement in retail rate filings with the ICC. In March 2011, FERC issued an order authorizing the proposed rates to take effect, subject to refund when the final rates are determined. Ameren Illinois has reached settlements with four of its nine wholesale customers, which have been approved by FERC and for which refunds have been issued. The impasse with the remaining five wholesale customers is awaiting final FERC action. In November 2012, a FERC administrative law judge issued an initial decision, which is now pending before FERC. The timing of a decision from FERC is uncertain and subsequent appeals are possible. In accordance with the administrative law judge's initial decision, Ameren and Ameren Illinois have both included on their respective balance sheets in “Current regulatory liabilities” an estimate of $16 million and $13 million as of June 30, 2014, and December 31, 2013, respectively, for the refund due to the remaining wholesale customers relating to billings since March 2011. Ameren Illinois Electric Transmission Rate Refund In July 2012, FERC issued an order concluding that Ameren Illinois improperly included acquisition premiums, including goodwill, in determining the common equity used in its electric transmission formula rate, and thereby inappropriately recovered a higher amount from its electric transmission customers. The order required Ameren Illinois to make refunds to customers for such improperly included amounts. In August 2012, Ameren Illinois filed a request for a rehearing of this order. Ameren Illinois submitted a refund report in November 2012 and concluded that no refund was warranted. Several wholesale customers filed a protest with FERC regarding Ameren's conclusion that no refund was warranted. In June 2013, FERC issued an order that rejected Ameren Illinois' November 2012 refund report and provided guidance as to the filing of a new refund report. In July 2013, Ameren Illinois filed a revised refund report based on the guidance provided in the June 2013 order, as well as a request for a rehearing of that order. Ameren Illinois' July 2013 refund report also concluded that no refund was warranted. In June 2014, FERC issued an order that denied Ameren Illinois’ rehearing requests of the July 2012 order and the June 2013 order. Separately, in June 2014, FERC issued an order that established hearing and settlement procedures for Ameren Illinois’ July 2013 refund report. In July 2014, Ameren Illinois filed an appeal of FERC’s orders denying rehearing of the July 2012 and June 2013 orders with the United States Court of Appeals for the District of Columbia Circuit. Also in July 2014, Ameren Illinois separately filed a request for rehearing with FERC of its June 2014 order regarding the July 2013 refund report. Ameren Illinois estimates the maximum pretax charge to earnings for this possible refund obligation through December 31, 2014, would be $19 million, before interest charges. During the three months ended June 30, 2014, Ameren and Ameren Illinois recorded a $4 million reduction to “Operating Revenues - Electric” with a corresponding increase to “Current regulatory liabilities” for its estimate of the refund due to electric transmission customers based on the June 2014 order. If Ameren Illinois were to determine that a refund to its electric transmission customers in excess of the amount already recorded is probable, an additional charge to earnings would be recorded in the period in which that determination is made. FERC Complaint Case In November 2013, a customer group filed a complaint case with FERC seeking a reduction in the allowed return on common equity to 9.15%, as well as a limit on the common equity ratio, under the MISO tariff. Currently, the FERC-allowed return on common equity for MISO transmission owners is 12.38%. This complaint case could result in a reduction to Ameren Illinois' and ATXI's allowed return on common equity. That reduction could also result in a refund for transmission service revenues earned after the filing of the complaint case in November 2013. FERC has not issued an order in this case, and it is under no deadline to do so. In June 2014, FERC issued an order that reduced the base allowed return on common equity for New England transmission owners from 11.14% to 10.57% with rate incentives allowed up to 11.74%. The FERC order in the New England transmission owners’ case applied observable market data from October 2012 to March 2013 to determine the allowed return on common equity. Ameren believes some aspects of the FERC order in the New England transmission owners’ case may establish precedent in the pending MISO case. However, the calculation FERC used to establish the base allowed return on common equity, which is based on a unique time period for each complaint case, required multiple inputs based on observable market data specific to the utility industry and broader macroeconomic data, which are highly uncertain. Due to the wide range of potential outcomes and significant uncertainty regarding the inputs required in FERC’s calculation, the Ameren Companies cannot reasonably estimate the impact, if any, that a FERC ruling in the MISO complaint case could have on their allowed base return on common equity. If FERC lowered MISO’s allowed base return on equity to 10.57%, as established in the New England transmission owners’ case, with no additional rate incentives, the required refund for Ameren and Ameren Illinois would be $9 million and $7 million, respectively, from the filing of the complaint case in November 2013 through June 30, 2014. The estimated ongoing annual reduction in revenues if the MISO return on equity was 10.57% for Ameren and Ameren Illinois would be $16 million and $12 million, respectively. Ameren Missouri would not expect a reduction of its allowed base return on common equity to result in a material impact to its financial statements. If Ameren and Ameren Illinois were to determine that a refund to their electric transmission customers is probable and can be reasonably estimated, a charge to earnings would be recorded for the refund in the period in which that determination is made. Ameren Missouri Power Purchase Agreement with Entergy Beginning in 2005, FERC issued a series of orders addressing a complaint filed in 2001 by the Louisiana Public Service Commission against Entergy and certain of its affiliates. The complaint alleged unjust and unreasonable cost allocations. As a result of the FERC orders, Entergy began billing Ameren Missouri in 2007 for additional charges under a 165-megawatt power purchase agreement, which expired August 31, 2009. In May 2012, FERC issued an order stating that Entergy should not have included additional charges to Ameren Missouri under the power purchase agreement. Pursuant to the order, in June 2012, Entergy paid Ameren Missouri $31 million. In July 2012, Entergy filed an appeal of FERC's May 2012 orders to the United States Court of Appeals for the District of Columbia Circuit, which was subsequently dismissed on a procedural issue. In November 2013, Entergy refiled the appeal of FERC's May 2012 order with the United States Court of Appeals for the District of Columbia Circuit. Ameren is not able to predict when or how the court will rule on Entergy's appeal. The Louisiana Public Service Commission appealed FERC’s orders regarding Louisiana Public Service Commission’s complaint against Entergy Services, Inc. to the United States Court of Appeals for the District of Columbia Circuit. In April 2008, that court ordered further FERC proceedings regarding Louisiana Public Service Commission’s complaint. The court ordered FERC to explain its previous denial of retroactive refunds and the implementation of prospective charges. Ameren Missouri is unable to predict when or how FERC will respond to the court’s decisions. Ameren Missouri estimates that it could incur an additional expense of up to $25 million if FERC orders retroactive application for the years 2001 to 2005. Ameren Missouri believes that the likelihood of incurring any expense is not probable, and therefore no liability has been recorded as of June 30, 2014. Combined Construction and Operating License In 2008, Ameren Missouri filed an application with the NRC for a COL for a new nuclear unit at Ameren Missouri's existing Callaway County, Missouri, energy center site. In 2009, Ameren Missouri suspended its efforts to build a new nuclear unit at its existing Missouri nuclear energy center site, and the NRC suspended review of the COL application. Ameren Missouri estimated the total cost required to obtain a small modular reactor COL to be $80 million to $120 million. As of June 30, 2014, Ameren Missouri had capitalized investments of $69 million for the development of a new nuclear energy center. Ameren Missouri is currently evaluating all potential nuclear technologies in order to maintain an option for nuclear power in the future. All of Ameren Missouri's capitalized investments for the development of a new nuclear energy center will remain capitalized while management pursues options to maximize the value of its investment. If efforts to license additional nuclear generation are abandoned or management concludes it is probable the costs incurred will be disallowed in rates, a charge to earnings would be recognized in the period in which that determination is made. Pumped-storage Hydroelectric Energy Center Relicensing In June 2008, Ameren Missouri filed a relicensing application with FERC to operate its Taum Sauk pumped-storage hydroelectric energy center. The existing FERC license expired on June 30, 2010. In July 2010, Ameren Missouri received a license extension that allowed Taum Sauk to continue operations until FERC issued a new license. In July 2014, FERC issued an order authorizing Ameren Missouri to operate its Taum Sauk pumped-storage hydroelectric energy center for an additional 30 years through July 2044.

RATE AND REGULATORY MATTERS

Below is a summary of updates to significant regulatory proceedings and related lawsuits. See also Note 2 - Rate and Regulatory Matters under Part II, Item 8, of the Form 10-K. We are unable to predict the ultimate outcome of these matters, the timing of the final decisions of the various agencies and courts, or the impact on our results of operations, financial position, or liquidity.

Missouri

2014 Electric Rate Case

In July 2014, Ameren Missouri filed a request with the MoPSC seeking approval to increase its annual revenues for electric service by $264 million. The rate request seeks recovery of increased net energy costs and rebates provided for customer-installed solar generation, as well as recovery of and a return on additional electric infrastructure investments made for the benefit of Ameren Missouri’s customers. Plant additions to rate base since the last electric rate order are expected to total approximately $1.4 billion through the anticipated true-up date in this rate case and include electric infrastructure investments for upgrades to the electrostatic precipitators at the coal-fired Labadie energy center to meet more stringent environmental regulations, the replacement of the nuclear reactor vessel head at the Callaway energy center in order to ensure continued safe and dependable operations, two new substations in St. Louis, and the O’Fallon energy center, which will be Missouri’s largest investor-owned utility solar facility, among other additions. Approximately $127 million of the request relates to an increase in net energy costs above the current levels included in base rates previously authorized by the MoPSC in its December 2012 electric rate order, 95% of which, absent initiation of this general rate proceeding, would have been reflected in rate adjustments implemented under Ameren Missouri’s existing FAC. The electric rate increase request is based on a 10.4% return on equity, a capital structure composed of 51.6% common equity, an electric rate base for Ameren Missouri of $7.3 billion, and a test year ended March 31, 2014, with certain pro-forma adjustments expected through the anticipated true-up date of December 31, 2014.

As a part of its filing, Ameren Missouri also requested continued use of the FAC and the regulatory tracking mechanisms for storm costs, vegetation management/infrastructure inspection costs, pension and postretirement benefits, and uncertain income tax positions that the MoPSC previously authorized in earlier electric rate orders.

The MoPSC proceeding relating to the proposed electric service rate changes will take place over a period of up to 11 months and a decision by the MoPSC in such proceeding is expected by May 2015, with rates effective by June 2015. Ameren Missouri cannot predict the level of any electric service rate change the MoPSC may approve, when any rate change may go into effect or whether any rate increase that may eventually be approved will be sufficient for Ameren Missouri to recover its costs and earn a reasonable return on its investments when the increase goes into effect.

Accounting Authority Order

In July 2011, Ameren Missouri filed a request with the MoPSC for an accounting authority order that would allow Ameren Missouri to defer fixed costs totaling $36 million that were not previously recovered from Noranda as a result of the loss of load caused by the severe 2009 ice storm for potential recovery in a future electric rate case. In November 2013, the MoPSC issued an accounting authority order that allowed Ameren Missouri to seek recovery of these fixed costs in an electric rate case. Ameren Missouri’s July 2014 electric rate case filing requested recovery of these fixed costs over five years. In February 2014, MIEC and MoOPC filed appeals of the MoPSC’s November 2013 accounting authority order with the Missouri Court of Appeals, Western District. Ameren Missouri has not recorded any potential revenue associated with this accounting authority order.

Earnings Complaint and Rate Shift Complaint Cases

In February 2014, Ameren Missouri’s largest customer, Noranda, and 37 residential customers filed an earnings complaint case and a rate shift complaint case with the MoPSC.

In the earnings complaint case, Noranda and the residential customers asserted that Ameren Missouri’s electric service business is earning more than the 9.8% return on common equity authorized in the MoPSC's December 2012 electric rate order. Noranda and the residential customers are currently requesting the MoPSC approve a $49 million reduction to Ameren Missouri’s annual revenue requirement. Included in Noranda’s request is a reduction of Ameren Missouri’s authorized return on common equity to 9.4%. The MoPSC staff filed testimony in this case that recommended no reduction to Ameren Missouri’s annual revenue requirement. The MoOPC and MIEC intervened in the earnings complaint case. The rate shift complaint case seeks to reduce Noranda's electric rates with an offsetting increase in electric rates for Ameren Missouri's other customers. While the rate shift proposal is revenue neutral to Ameren Missouri, Ameren Missouri does not believe that the proposed reduction to Noranda's electric rates, which would result in rates that are significantly below Ameren Missouri's cost of service, is appropriate or in the best interests of Ameren Missouri's other electric customers.

While the MoPSC has no time requirement by which it must issue orders in these cases, it has adopted procedural schedules that Ameren Missouri expects would render a decision in the rate shift case during the third quarter of 2014, and in the earnings complaint case by September 26, 2014. Ameren Missouri does not believe that a reduction in electric service rates is justified and filed testimony that supports that position, which is consistent with Ameren Missouri’s July 2014 electric rate case filing.

Illinois

IEIMA

Under the provisions of the IEIMA, Ameren Illinois’ electric delivery service rates are subject to an annual revenue requirement reconciliation to its actual costs. Throughout each year, Ameren Illinois records a regulatory asset or a regulatory liability and a corresponding increase or decrease to operating revenues for any differences between the revenue requirement in effect for customer billings for that year and its estimate of the probable increase or decrease in the revenue requirement expected to ultimately be approved by the ICC based on that year's actual costs incurred. As of June 30, 2014, Ameren Illinois had recorded a regulatory asset of $42 million and $64 million, respectively, to reflect its expected 2014 and 2013 revenue requirement reconciliation adjustments, with interest. As of June 30, 2014, Ameren Illinois had recorded a regulatory liability of $35 million to reflect its 2012 revenue requirement reconciliation adjustment, with interest, which will be refunded to customers during 2014.

In September 2012 and December 2012, the ICC issued orders in Ameren Illinois’ IEIMA performance-based formula rate filings. Ameren Illinois appealed both orders to the Appellate Court of the Fourth District of Illinois. The primary issues Ameren Illinois appealed were the rate treatment of accumulated deferred income taxes and vacation obligations as well as the calculation of Ameren Illinois’ capital structure. In December 2013, the appellate court rendered its decision upholding the ICC’s September and December 2012 orders. Ameren Illinois filed an appeal to the Illinois Supreme Court in March 2014. In May 2014, the Illinois Supreme Court denied Ameren Illinois’ appeal.

In December 2013, the ICC issued an order in Ameren Illinois' annual update filing, which was based on 2012 recoverable costs and expected net plant additions for 2013. The ICC order established rates for 2014. In February 2014, Ameren Illinois filed an appeal to the Appellate Court of the Fourth District of Illinois regarding the calculation of its capital structure and the rate treatment of accumulated deferred income taxes related to the transfer of former Ameren Missouri assets in Illinois to Ameren Illinois. Ameren Illinois will not pursue the calculation of its capital structure in its appeal as a result of the Illinois Supreme Court ruling discussed above in May 2014. Ameren Illinois will continue its appeal of the rate treatment of accumulated deferred income taxes.

In April 2014, Ameren Illinois filed with the ICC its annual electric delivery service formula rate update to establish the revenue requirement used to set rates for 2015. Pending ICC approval, Ameren Illinois’ update filing, as revised in July 2014, will result in a $205 million increase in Ameren Illinois’ electric delivery service revenue requirement beginning in January 2015. This update reflects an increase to the annual formula rate based on 2013 actual costs and expected net plant additions for 2014, an increase to include the annual reconciliation of the revenue requirement in effect for 2013 to the actual costs incurred in that year, and an increase resulting from the conclusion of a refund to customers in 2014 for the 2012 revenue requirement reconciliation. In July 2014, the ICC staff submitted its calculation of the revenue requirement included in Ameren Illinois’ update filling. The ICC staff recommended adjustments that would result in a $202 million increase in Ameren Illinois’ electric delivery service revenue requirement. An ICC decision on this April 2014 filing is expected by December 2014.

2013 Natural Gas Delivery Service Rate Case

In December 2013, the ICC issued a rate order that approved an increase in revenues for natural gas delivery service of $32 million. The revenue increase was based on a 9.1% return on equity, a capital structure composed of 51.7% common equity, and a rate base of $1.1 billion. The rate order was based on a 2014 future test year. The rate changes became effective January 1, 2014. In March 2014, Ameren Illinois filed an appeal of the allowed return on common equity included in the ICC's order and is also appealing the rate treatment of accumulated deferred income taxes related to the transfer of former Ameren Missouri assets in Illinois to Ameren Illinois with the Appellate Court of the Fourth District of Illinois. Ameren Illinois sought a 10.4% return on common equity in this rate case.

Federal

2011 Wholesale Distribution Rate Case

In January 2011, Ameren Illinois filed a request with FERC to increase its annual revenues for electric delivery service for its wholesale customers. These wholesale distribution revenues are treated as a deduction from Ameren Illinois’ revenue requirement in retail rate filings with the ICC. In March 2011, FERC issued an order authorizing the proposed rates to take effect, subject to refund when the final rates are determined. Ameren Illinois has reached settlements with four of its nine wholesale customers, which have been approved by FERC and for which refunds have been issued. The impasse with the remaining five wholesale customers is awaiting final FERC action. In November 2012, a FERC administrative law judge issued an initial decision, which is now pending before FERC. The timing of a decision from FERC is uncertain and subsequent appeals are possible. In accordance with the administrative law judge's initial decision, Ameren and Ameren Illinois have both included on their respective balance sheets in “Current regulatory liabilities” an estimate of $16 million and $13 million as of June 30, 2014, and December 31, 2013, respectively, for the refund due to the remaining wholesale customers relating to billings since March 2011.

Ameren Illinois Electric Transmission Rate Refund

In July 2012, FERC issued an order concluding that Ameren Illinois improperly included acquisition premiums, including goodwill, in determining the common equity used in its electric transmission formula rate, and thereby inappropriately recovered a higher amount from its electric transmission customers. The order required Ameren Illinois to make refunds to customers for such improperly included amounts. In August 2012, Ameren Illinois filed a request for a rehearing of this order.

Ameren Illinois submitted a refund report in November 2012 and concluded that no refund was warranted. Several wholesale customers filed a protest with FERC regarding Ameren's conclusion that no refund was warranted. In June 2013, FERC issued an order that rejected Ameren Illinois' November 2012 refund report and provided guidance as to the filing of a new refund report. In July 2013, Ameren Illinois filed a revised refund report based on the guidance provided in the June 2013 order, as well as a request for a rehearing of that order. Ameren Illinois' July 2013 refund report also concluded that no refund was warranted.

In June 2014, FERC issued an order that denied Ameren Illinois’ rehearing requests of the July 2012 order and the June 2013 order. Separately, in June 2014, FERC issued an order that established hearing and settlement procedures for Ameren Illinois’ July 2013 refund report. In July 2014, Ameren Illinois filed an appeal of FERC’s orders denying rehearing of the July 2012 and June 2013 orders with the United States Court of Appeals for the District of Columbia Circuit. Also in July 2014, Ameren Illinois separately filed a request for rehearing with FERC of its June 2014 order regarding the July 2013 refund report.

Ameren Illinois estimates the maximum pretax charge to earnings for this possible refund obligation through December 31, 2014, would be $19 million, before interest charges. During the three months ended June 30, 2014, Ameren and Ameren Illinois recorded a $4 million reduction to “Operating Revenues - Electric” with a corresponding increase to “Current regulatory liabilities” for its estimate of the refund due to electric transmission customers based on the June 2014 order. If Ameren Illinois were to determine that a refund to its electric transmission customers in excess of the amount already recorded is probable, an additional charge to earnings would be recorded in the period in which that determination is made.

FERC Complaint Case

In November 2013, a customer group filed a complaint case with FERC seeking a reduction in the allowed return on common equity to 9.15%, as well as a limit on the common equity ratio, under the MISO tariff. Currently, the FERC-allowed return on common equity for MISO transmission owners is 12.38%. This complaint case could result in a reduction to Ameren Illinois' and ATXI's allowed return on common equity. That reduction could also result in a refund for transmission service revenues earned after the filing of the complaint case in November 2013. FERC has not issued an order in this case, and it is under no deadline to do so.

In June 2014, FERC issued an order that reduced the base allowed return on common equity for New England transmission owners from 11.14% to 10.57% with rate incentives allowed up to 11.74%. The FERC order in the New England transmission owners’ case applied observable market data from October 2012 to March 2013 to determine the allowed return on common equity. Ameren believes some aspects of the FERC order in the New England transmission owners’ case may establish precedent in the pending MISO case. However, the calculation FERC used to establish the base allowed return on common equity, which is based on a unique time period for each complaint case, required multiple inputs based on observable market data specific to the utility industry and broader macroeconomic data, which are highly uncertain. Due to the wide range of potential outcomes and significant uncertainty regarding the inputs required in FERC’s calculation, the Ameren Companies cannot reasonably estimate the impact, if any, that a FERC ruling in the MISO complaint case could have on their allowed base return on common equity.

If FERC lowered MISO’s allowed base return on equity to 10.57%, as established in the New England transmission owners’ case, with no additional rate incentives, the required refund for Ameren and Ameren Illinois would be $9 million and $7 million, respectively, from the filing of the complaint case in November 2013 through June 30, 2014. The estimated ongoing annual reduction in revenues if the MISO return on equity was 10.57% for Ameren and Ameren Illinois would be $16 million and $12 million, respectively. Ameren Missouri would not expect a reduction of its allowed base return on common equity to result in a material impact to its financial statements. If Ameren and Ameren Illinois were to determine that a refund to their electric transmission customers is probable and can be reasonably estimated, a charge to earnings would be recorded for the refund in the period in which that determination is made.

Ameren Missouri Power Purchase Agreement with Entergy

Beginning in 2005, FERC issued a series of orders addressing a complaint filed in 2001 by the Louisiana Public Service Commission against Entergy and certain of its affiliates. The complaint alleged unjust and unreasonable cost allocations. As a result of the FERC orders, Entergy began billing Ameren Missouri in 2007 for additional charges under a 165-megawatt power purchase agreement, which expired August 31, 2009. In May 2012, FERC issued an order stating that Entergy should not have included additional charges to Ameren Missouri under the power purchase agreement. Pursuant to the order, in June 2012, Entergy paid Ameren Missouri $31 million. In July 2012, Entergy filed an appeal of FERC's May 2012 orders to the United States Court of Appeals for the District of Columbia Circuit, which was subsequently dismissed on a procedural issue. In November 2013, Entergy refiled the appeal of FERC's May 2012 order with the United States Court of Appeals for the District of Columbia Circuit. Ameren is not able to predict when or how the court will rule on Entergy's appeal.

The Louisiana Public Service Commission appealed FERC’s orders regarding Louisiana Public Service Commission’s complaint against Entergy Services, Inc. to the United States Court of Appeals for the District of Columbia Circuit. In April 2008, that court ordered further FERC proceedings regarding Louisiana Public Service Commission’s complaint. The court ordered FERC to explain its previous denial of retroactive refunds and the implementation of prospective charges. Ameren Missouri is unable to predict when or how FERC will respond to the court’s decisions. Ameren Missouri estimates that it could incur an additional expense of up to $25 million if FERC orders retroactive application for the years 2001 to 2005. Ameren Missouri believes that the likelihood of incurring any expense is not probable, and therefore no liability has been recorded as of June 30, 2014.

Combined Construction and Operating License

In 2008, Ameren Missouri filed an application with the NRC for a COL for a new nuclear unit at Ameren Missouri's existing Callaway County, Missouri, energy center site. In 2009, Ameren Missouri suspended its efforts to build a new nuclear unit at its existing Missouri nuclear energy center site, and the NRC suspended review of the COL application.

Ameren Missouri estimated the total cost required to obtain a small modular reactor COL to be $80 million to $120 million. As of June 30, 2014, Ameren Missouri had capitalized investments of $69 million for the development of a new nuclear energy center. Ameren Missouri is currently evaluating all potential nuclear technologies in order to maintain an option for nuclear power in the future.

All of Ameren Missouri's capitalized investments for the development of a new nuclear energy center will remain capitalized while management pursues options to maximize the value of its investment. If efforts to license additional nuclear generation are abandoned or management concludes it is probable the costs incurred will be disallowed in rates, a charge to earnings would be recognized in the period in which that determination is made.

Pumped-storage Hydroelectric Energy Center Relicensing

In June 2008, Ameren Missouri filed a relicensing application with FERC to operate its Taum Sauk pumped-storage hydroelectric energy center. The existing FERC license expired on June 30, 2010. In July 2010, Ameren Missouri received a license extension that allowed Taum Sauk to continue operations until FERC issued a new license. In July 2014, FERC issued an order authorizing Ameren Missouri to operate its Taum Sauk pumped-storage hydroelectric energy center for an additional 30 years through July 2044.