Regulatory Matters	12 Months Ended
Regulatory Matters	Dec. 31, 2012
Regulatory Matters	3. REGULATORY MATTERS General IPL is subject to regulation by the IURC as to its services and facilities, the valuation of property, the construction, purchase, or lease of electric generating facilities, the classification of accounts, rates of depreciation, retail rates and charges, the issuance of securities (other than evidences of indebtedness payable less than twelve months after the date of issue), the acquisition and sale of some public utility properties or securities and certain other matters. In addition, IPL is subject to the jurisdiction of the FERC with respect to short-term borrowing not regulated by the IURC, the sale of electricity at wholesale and the transmission of electric energy in interstate commerce, the classification of accounts, reliability standards, and the acquisition and sale of utility property in certain circumstances as provided by the Federal Power Act. As a regulated entity, IPL is required to use certain accounting methods prescribed by regulatory bodies which may differ from those accounting methods required to be used by unregulated entities. IPL is also affected by the regulatory jurisdiction of the U.S. Environmental Protection Agency ("EPA") at the federal level, and the Indiana Department of Environmental Management at the state level. Other significant regulatory agencies affecting IPL include, but are not limited to, North American Electric Reliability Corporation, the U.S. Department of Labor and the Indiana Occupational Safety and Health Administration. Fuel Adjustment Charge and Authorized Annual Jurisdictional Net Operating Income IPL may apply to the IURC for a change in IPL's fuel charge every three months to recover IPL's estimated fuel costs, including the energy portion of purchased power costs, which may be above or below the levels included in IPL's basic rates and charges. IPL must present evidence in each FAC proceeding that it has made every reasonable effort to acquire fuel and generate or purchase power or both so as to provide electricity to its retail customers at the lowest fuel cost reasonably possible. Independent of the IURC's ability to review basic rates and charges, Indiana law requires electric utilities under the jurisdiction of the IURC to meet operating expense and income test requirements as a condition for approval of requested changes in the FAC. Additionally, customer refunds may result if a utility's rolling twelve month operating income, determined at quarterly measurement dates, exceeds a utility's authorized annual jurisdictional net operating income and there are not sufficient applicable cumulative net operating income deficiencies against which the excess rolling twelve month jurisdictional net operating income can be offset. Environmental Compliance Cost Recovery Adjustment ("ECCRA") IPL may apply to the IURC for approval of a rate adjustment known as the Environmental Compliance Cost Recovery Adjustment ("ECCRA") every six months to recover costs to install and/or upgrade Clean Coal Technology ("CCT") equipment. The total amount of IPL's CCT equipment approved for ECCRA recovery as of December 31, 2012 was $618.8 million. The jurisdictional revenue requirement that was approved by the IURC to be included in IPL's rates for the six month period from September 2012 through February 2013 was $52.9 million. During the years ended December 31, 2012, 2011 and 2010, we made total CCT expenditures of $15.0 million, $64.4 million, and $53.1 million, respectively. The vast majority of such costs are recoverable through our ECCRA filings. The EPA released the final Mercury and Air Toxics Standards ("MATS") rule in December 2011 to address hazardous air pollutant emissions from certain electric generating power plants, and IPL management has developed a plan to comply with this new rule, as discussed in "Environmental Matters - MATS." We will seek and expect to recover through our environmental rate adjustment mechanism, all operating and capital expenditures related to compliance with MATS; however, there can be no assurance that we will be successful in that regard. Demand-Side Management and IPL's Smart Energy Project On December 9, 2009, the IURC issued a Generic Demand Side Management ("DSM") Order that found that electric utilities subject to its jurisdiction must meet an overall goal of annual cost-effective DSM programs that reduce retail kilowatt hours ("kWh") sales (as compared to what sales would have been excluding the DSM programs) of 2% per year by 2019 (beginning in 2010 at 0.3% and growing to 2.0% in 2019, and subject to certain adjustments). The IURC also found that all jurisdictional electric utilities have to participate in five initial, statewide core DSM programs, which are administered by a third party administrator. Consequently, our DSM spending, both capital and operating, began increasing significantly in 2010 and will continue to increase significantly going forward, which will likely reduce our retail energy sales and the associated revenues. In October 2010, IPL filed a petition with the IURC for approval of its plan to comply with the IURC's Generic DSM Order. In November 2011, IPL received approval from the IURC for this plan. Current spending approvals in effect through December 31, 2013 total $54.5 million and include the opportunity for performance based incentives. In August 2012, the IURC approved a one year extension of the contract with the current state-wide third party administrator to continue providing certain DSM programs for IPL and other jurisdictional utilities through December 31, 2014. In 2010, IPL was awarded a smart grid investment grant for $20 million as part of its $48.9 million Smart Energy Project (including smart grid technology), which will provide its customers with tools to help them more efficiently use electricity and upgrade IPL's electric delivery system infrastructure. Under the grant, the U.S. Department of Energy is providing nontaxable reimbursements to IPL for up to $20 million of capitalized costs associated with IPL's Smart Energy Project. These reimbursements are being accounted for as a reduction of the capitalized Smart Energy Project costs. Through December 31, 2012, we have received total grant reimbursements of $19.1 million since the 2010 project inception. Tree Trimming Practices Investigation In February 2009, an IPL customer filed a complaint claiming our tree trimming practices were unreasonable and expressed concerns with language contained in our tariff that addressed our tree trimming and tree removal rights. Subsequently, the IURC initiated a generic investigation into electric utility tree trimming practices and tariffs in Indiana. In November 2010, the IURC issued an order in the investigation, which imposed additional requirements on the conduct of tree trimming. The order included requirements on utilities to provide advance customer notice and obtain customer consent or additional easements if existing easements and rights of way are insufficient to permit pruning in accordance with the required industry standards or in the event that a tree would need to have more than 25% of its canopy removed. The order also directed that a rulemaking would be initiated to further address vegetation management practices. On July 7, 2011, the IURC issued an additional tree trimming order which did not provide the relief we were seeking, but clarified utility customer notice requirements and the relationship of the order to property rights and tariff requirements. It also clarified that in cases of emergency or public safety, utilities may, without customer consent, remove more than 25% of a tree or trim beyond existing easement or right of way boundaries to remedy the situation. In July 2012, the IURC issued its final order in the tree trimming practices rulemaking, which was later approved by the Indiana governor and attorney general and became law in October 2012. IPL is implementing procedures to ensure it appropriately complies with the requirements of the new rule that addresses notification, dispute resolution and other activities associated with its vegetation management practices. The requirements of the new ruling are similar to current practices. However, the actual cost impact of the rule will not be known until we have experience operating under its terms. Renewable Power Purchase Agreements We are committed under a power purchase agreement to purchase approximately 100 MW of wind generated electricity through 2029 from a wind project in Indiana. We are also committed under another agreement to purchase approximately 200 MW of wind generated electricity for 20 years from a project in Minnesota, which began commercial operation in October 2011. We have authority from the IURC to recover the costs for both of these agreements through an adjustment mechanism administered within the FAC. We also expect to have up to 100 MW of solar generated electricity under contract in 2013, subject to approval by the IURC. MISO Real Time Revenue Sufficiency Guarantee MISO collects Revenue Sufficiency Guarantee ("RSG") charges from market participants to pay for generation dispatched when the costs of such generation are not recovered in the market clearing price. Over the past several years, there have been disagreements between interested parties regarding the calculation methodology for RSG charges and how such charges should be allocated to the individual MISO participants. MISO has changed their methodology multiple times. Per past FERC orders, in December 2008, MISO filed with the FERC its proposed revisions and clarifications to the calculation of the RSG charges and had begun to use its new methodology in January 2009, including making resettlements of previous calculations. In the second quarter of 2009, the FERC withdrew its previous orders related to RSG charges and further directed MISO to cease the ongoing market resettlements and refund process and to reconcile the amounts paid and collected in order to return each market participant to the financial state it was in before the refund process began. This has the potential implication that IPL would no longer be entitled to refunds that were due to IPL under the previous order for periods between April 1, 2005 and November 4, 2007. In July 2009, IPL filed a Request for Clarification or alternately a Request for Rehearing on this issue alone. In addition to our requests, other interested parties have expressed interest in a different model of allocating RSG charges. Another factor that affects how RSG charges impact IPL is our ability to recover such costs from our customers through our FAC and/or in a future basic rate case proceeding. Under the methodology currently in effect, RSG charges have little effect on IPL's financial statements as the vast majority of such charges are considered to be fuel costs and are recoverable through IPL's FAC, while the remainder are being deferred for future recovery in accordance with generally accepted accounting principles in the U.S. However, the IURC's orders in IPL's FAC 77, 78 and 79 proceedings approved IPL's FAC factor on an interim basis, subject to refund, pending the outcome of the FERC proceeding regarding RSG charges and any subsequent appeals therefrom. On August 30, 2010, FERC issued an order approving the RSG Redesign as previously filed under Section 206 on February 23, 2009 and required MISO to make a compliance filing with the changes. On October 29, 2010 MISO made its compliance filing regarding the RSG Redesign, and indicated that it would subsequently file under Section 205 modifications to the RSG Redesign rate. MISO also indicated it expected to be ready to implement the RSG Redesign rate on March 1, 2011. On February 15, 2011, MISO filed to amend its December 1, 2010 filing modifying the RSG Redesign rate, to change the effective date of the proposed modifications to April 1, 2011. FERC issued its order partially accepting the filings on March 31, 2011. On May 2, 2011, MISO submitted a request for rehearing or clarification of FERC's March 31, 2011 order regarding the allocation of the cost of RSG. As a result, it is not possible to predict how these proceedings will ultimately impact IPL, but we do not believe they will have a material impact on our financial statements. MISO Transmission Expansion Cost Sharing and FERC Order 1000 Beginning in 2007, MISO transmission system owner members including IPL began to share the costs of transmission expansion projects with other transmission system owner members after such projects were approved by the MISO board of directors. Upon approval by the MISO board of directors the transmission system owner members must make a good faith effort to build and/or pay for the projects. Costs allocated to IPL for the projects of other transmission system owner members are collected by MISO per their tariff. See also Senate Bill 251 below under "Environmental Matters." On July 21, 2011, the FERC issued Order 1000, amending the transmission planning and cost allocation requirements established in Order No. 890. Through Order 1000, the FERC: (1) requires public utility transmission providers to participate in a regional transmission planning process and produce a regional transmission plan; (2) requires public utility transmission providers to amend their open access transmission tariffs to describe how public policy requirements will be considered in local and regional transmission planning processes; (3) removes the federal right of first refusal for certain transmission facilities; and (4) seeks to improve coordination between neighboring transmission planning regions for interregional facilities. MISO's approved tariff in part already complies with Order 1000. However, Order 1000 will result in changes to transmission expansion costs charged to us by MISO. Such changes relate to public policy requirements for transmission expansion within the MISO footprint, such as to comply with renewable mandates of other states within the footprint. These charges are difficult to estimate, but are expected to be material to us within a few years; however, it is probable, but not certain, that these costs will be recoverable, subject to IURC approval. Through December 31, 2012, we have deferred as a regulatory asset $2.2 million of MISO transmission expansion costs.
Indianapolis Power And Light Company [Member]
Regulatory Matters	3. REGULATORY MATTERS General IPL is subject to regulation by the IURC as to its services and facilities, the valuation of property, the construction, purchase, or lease of electric generating facilities, the classification of accounts, rates of depreciation, retail rates and charges, the issuance of securities (other than evidences of indebtedness payable less than twelve months after the date of issue), the acquisition and sale of some public utility properties or securities and certain other matters. In addition, IPL is subject to the jurisdiction of the FERC with respect to short-term borrowing not regulated by the IURC, the sale of electricity at wholesale and the transmission of electric energy in interstate commerce, the classification of accounts, reliability standards, and the acquisition and sale of utility property in certain circumstances as provided by the Federal Power Act. As a regulated entity, IPL is required to use certain accounting methods prescribed by regulatory bodies which may differ from those accounting methods required to be used by unregulated entities. IPL is also affected by the regulatory jurisdiction of the U.S. Environmental Protection Agency ("EPA") at the federal level, and the Indiana Department of Environmental Management at the state level. Other significant regulatory agencies affecting IPL include, but are not limited to, North American Electric Reliability Corporation, the U.S. Department of Labor and the Indiana Occupational Safety and Health Administration. Fuel Adjustment Charge and Authorized Annual Jurisdictional Net Operating Income IPL may apply to the IURC for a change in IPL's fuel charge every three months to recover IPL's estimated fuel costs, including the energy portion of purchased power costs, which may be above or below the levels included in IPL's basic rates and charges. IPL must present evidence in each FAC proceeding that it has made every reasonable effort to acquire fuel and generate or purchase power or both so as to provide electricity to its retail customers at the lowest fuel cost reasonably possible. Independent of the IURC's ability to review basic rates and charges, Indiana law requires electric utilities under the jurisdiction of the IURC to meet operating expense and income test requirements as a condition for approval of requested changes in the FAC. Additionally, customer refunds may result if a utility's rolling twelve month operating income, determined at quarterly measurement dates, exceeds a utility's authorized annual jurisdictional net operating income and there are not sufficient applicable cumulative net operating income deficiencies against which the excess rolling twelve month jurisdictional net operating income can be offset. Environmental Compliance Cost Recovery Adjustment ("ECCRA") IPL may apply to the IURC for approval of a rate adjustment known as the Environmental Compliance Cost Recovery Adjustment ("ECCRA") every six months to recover costs to install and/or upgrade Clean Coal Technology ("CCT") equipment. The total amount of IPL's CCT equipment approved for ECCRA recovery as of December 31, 2012 was $618.8 million. The jurisdictional revenue requirement that was approved by the IURC to be included in IPL's rates for the six month period from September 2012 through February 2013 was $52.9 million. During the years ended December 31, 2012, 2011 and 2010, we made total CCT expenditures of $15.0 million, $64.4 million, and $53.1 million, respectively. The vast majority of such costs are recoverable through our ECCRA filings. The EPA released the final Mercury and Air Toxics Standards ("MATS") rule in December 2011 to address hazardous air pollutant emissions from certain electric generating power plants, and IPL management has developed a plan to comply with this new rule, as discussed in "Environmental Matters - MATS." We will seek and expect to recover through our environmental rate adjustment mechanism, all operating and capital expenditures related to compliance with MATS; however, there can be no assurance that we will be successful in that regard. Demand-Side Management and IPL's Smart Energy Project On December 9, 2009, the IURC issued a Generic Demand Side Management ("DSM") Order that found that electric utilities subject to its jurisdiction must meet an overall goal of annual cost-effective DSM programs that reduce retail kilowatt hours ("kWh") sales (as compared to what sales would have been excluding the DSM programs) of 2% per year by 2019 (beginning in 2010 at 0.3% and growing to 2.0% in 2019, and subject to certain adjustments). The IURC also found that all jurisdictional electric utilities have to participate in five initial, statewide core DSM programs, which are administered by a third party administrator. Consequently, our DSM spending, both capital and operating, began increasing significantly in 2010 and will continue to increase significantly going forward, which will likely reduce our retail energy sales and the associated revenues. In October 2010, IPL filed a petition with the IURC for approval of its plan to comply with the IURC's Generic DSM Order. In November 2011, IPL received approval from the IURC for this plan. Current spending approvals in effect through December 31, 2013 total $54.5 million and include the opportunity for performance based incentives. In August 2012, the IURC approved a one year extension of the contract with the current state-wide third party administrator to continue providing certain DSM programs for IPL and other jurisdictional utilities through December 31, 2014. In 2010, IPL was awarded a smart grid investment grant for $20 million as part of its $48.9 million Smart Energy Project (including smart grid technology), which will provide its customers with tools to help them more efficiently use electricity and upgrade IPL's electric delivery system infrastructure. Under the grant, the U.S. Department of Energy is providing nontaxable reimbursements to IPL for up to $20 million of capitalized costs associated with IPL's Smart Energy Project. These reimbursements are being accounted for as a reduction of the capitalized Smart Energy Project costs. Through December 31, 2012, we have received total grant reimbursements of $19.1 million since the 2010 project inception. Tree Trimming Practices Investigation In February 2009, an IPL customer filed a complaint claiming our tree trimming practices were unreasonable and expressed concerns with language contained in our tariff that addressed our tree trimming and tree removal rights. Subsequently, the IURC initiated a generic investigation into electric utility tree trimming practices and tariffs in Indiana. In November 2010, the IURC issued an order in the investigation, which imposed additional requirements on the conduct of tree trimming. The order included requirements on utilities to provide advance customer notice and obtain customer consent or additional easements if existing easements and rights of way are insufficient to permit pruning in accordance with the required industry standards or in the event that a tree would need to have more than 25% of its canopy removed. The order also directed that a rulemaking would be initiated to further address vegetation management practices. On July 7, 2011, the IURC issued an additional tree trimming order which did not provide the relief we were seeking, but clarified utility customer notice requirements and the relationship of the order to property rights and tariff requirements. It also clarified that in cases of emergency or public safety, utilities may, without customer consent, remove more than 25% of a tree or trim beyond existing easement or right of way boundaries to remedy the situation. In July 2012, the IURC issued its final order in the tree trimming practices rulemaking, which was later approved by the Indiana governor and attorney general and became law in October 2012. IPL is implementing procedures to ensure it appropriately complies with the requirements of the new rule that addresses notification, dispute resolution and other activities associated with its vegetation management practices. The requirements of the new ruling are similar to current practices. However, the actual cost impact of the rule will not be known until we have experience operating under its terms. Renewable Power Purchase Agreements We are committed under a power purchase agreement to purchase approximately 100 MW of wind generated electricity through 2029 from a wind project in Indiana. We are also committed under another agreement to purchase approximately 200 MW of wind generated electricity for 20 years from a project in Minnesota, which began commercial operation in October 2011. We have authority from the IURC to recover the costs for both of these agreements through an adjustment mechanism administered within the FAC. We also expect to have up to 100 MW of solar generated electricity under contract in 2013, subject to approval by the IURC. MISO Real Time Revenue Sufficiency Guarantee MISO collects Revenue Sufficiency Guarantee ("RSG") charges from market participants to pay for generation dispatched when the costs of such generation are not recovered in the market clearing price. Over the past several years, there have been disagreements between interested parties regarding the calculation methodology for RSG charges and how such charges should be allocated to the individual MISO participants. MISO has changed their methodology multiple times. Per past FERC orders, in December 2008, MISO filed with the FERC its proposed revisions and clarifications to the calculation of the RSG charges and had begun to use its new methodology in January 2009, including making resettlements of previous calculations. In the second quarter of 2009, the FERC withdrew its previous orders related to RSG charges and further directed MISO to cease the ongoing market resettlements and refund process and to reconcile the amounts paid and collected in order to return each market participant to the financial state it was in before the refund process began. This has the potential implication that IPL would no longer be entitled to refunds that were due to IPL under the previous order for periods between April 1, 2005 and November 4, 2007. In July 2009, IPL filed a Request for Clarification or alternately a Request for Rehearing on this issue alone. In addition to our requests, other interested parties have expressed interest in a different model of allocating RSG charges. Another factor that affects how RSG charges impact IPL is our ability to recover such costs from our customers through our FAC and/or in a future basic rate case proceeding. Under the methodology currently in effect, RSG charges have little effect on IPL's financial statements as the vast majority of such charges are considered to be fuel costs and are recoverable through IPL's FAC, while the remainder are being deferred for future recovery in accordance with generally accepted accounting principles in the U.S. However, the IURC's orders in IPL's FAC 77, 78 and 79 proceedings approved IPL's FAC factor on an interim basis, subject to refund, pending the outcome of the FERC proceeding regarding RSG charges and any subsequent appeals therefrom. On August 30, 2010, FERC issued an order approving the RSG Redesign as previously filed under Section 206 on February 23, 2009 and required MISO to make a compliance filing with the changes. On October 29, 2010 MISO made its compliance filing regarding the RSG Redesign, and indicated that it would subsequently file under Section 205 modifications to the RSG Redesign rate. MISO also indicated it expected to be ready to implement the RSG Redesign rate on March 1, 2011. On February 15, 2011, MISO filed to amend its December 1, 2010 filing modifying the RSG Redesign rate, to change the effective date of the proposed modifications to April 1, 2011. FERC issued its order partially accepting the filings on March 31, 2011. On May 2, 2011, MISO submitted a request for rehearing or clarification of FERC's March 31, 2011 order regarding the allocation of the cost of RSG. As a result, it is not possible to predict how these proceedings will ultimately impact IPL, but we do not believe they will have a material impact on our financial statements. MISO Transmission Expansion Cost Sharing and FERC Order 1000 Beginning in 2007, MISO transmission system owner members including IPL began to share the costs of transmission expansion projects with other transmission system owner members after such projects were approved by the MISO board of directors. Upon approval by the MISO board of directors the transmission system owner members must make a good faith effort to build and/or pay for the projects. Costs allocated to IPL for the projects of other transmission system owner members are collected by MISO per their tariff. See also Senate Bill 251 below under "Environmental Matters." On July 21, 2011, the FERC issued Order 1000, amending the transmission planning and cost allocation requirements established in Order No. 890. Through Order 1000, the FERC: (1) requires public utility transmission providers to participate in a regional transmission planning process and produce a regional transmission plan; (2) requires public utility transmission providers to amend their open access transmission tariffs to describe how public policy requirements will be considered in local and regional transmission planning processes; (3) removes the federal right of first refusal for certain transmission facilities; and (4) seeks to improve coordination between neighboring transmission planning regions for interregional facilities. MISO's approved tariff in part already complies with Order 1000. However, Order 1000 will result in changes to transmission expansion costs charged to us by MISO. Such changes relate to public policy requirements for transmission expansion within the MISO footprint, such as to comply with renewable mandates of other states within the footprint. These charges are difficult to estimate, but are expected to be material to us within a few years; however, it is probable, but not certain, that these costs will be recoverable, subject to IURC approval. Through December 31, 2012, we have deferred as a regulatory asset $2.2 million of MISO transmission expansion costs.