Other Commitments And Contingencies	3 Months Ended
Mar. 31, 2016
Other Commitments and Contingencies [Abstract]
Commitments and Contingencies	Other Commitments and Contingencies A. Guarantees and Indemnities. As a part of normal business, NiSource and certain subsidiaries enter into various agreements providing financial or performance assurance to third parties on behalf of certain subsidiaries. Such agreements include guarantees and stand-by letters of credit. These agreements are entered into primarily to support or enhance the creditworthiness otherwise attributed to a subsidiary on a stand-alone basis, thereby facilitating the extension of sufficient credit to accomplish the subsidiaries’ intended commercial purposes. At March 31, 2016, NiSource had issued stand-by letters of credit of approximately $14.7 million for the benefit of third parties. B. Legal Proceedings. The Company is party to certain claims and legal proceedings arising in the ordinary course of business, none of which is deemed to be individually material at this time. Due to the inherent uncertainty of litigation, there can be no assurance that the resolution of any particular claim or proceeding would not have a material adverse effect on the Company’s results of operations, financial position or liquidity. If one or more of such matters were decided against the Company, the effects could be material to the Company’s results of operations in the period in which the Company would be required to record or adjust the related liability and could also be material to the Company’s cash flows in the periods the Company would be required to pay such liability. C. Environmental Matters. NiSource operations are subject to environmental statutes and regulations related to air quality, water quality, hazardous waste and solid waste. NiSource believes that it is in substantial compliance with the environmental regulations currently applicable to its operations. It is management's continued intent to address environmental issues in cooperation with regulatory authorities in such a manner as to achieve mutually acceptable compliance plans. However, there can be no assurance that fines and penalties will not be incurred. Management expects a significant portion of environmental assessment and remediation costs to be recoverable through rates for certain NiSource companies. As of March 31, 2016 and December 31, 2015, NiSource had recorded an accrual of approximately $122.0 million and $123.2 million, respectively, to cover environmental remediation at various sites. The current portion of this accrual is included in "Legal and environmental" in the Condensed Consolidated Balance Sheets (unaudited). The noncurrent portion is included in "Other noncurrent liabilities" in the Condensed Consolidated Balance Sheets (unaudited). NiSource accrues for costs associated with environmental remediation obligations when the incurrence of such costs is probable and the amounts can be reasonably estimated. The original estimates for cleanup may differ materially from the amount ultimately expended. The actual future expenditures depend on many factors, including currently enacted laws and regulations, the nature and extent of contamination, the method of cleanup and the availability of cost recovery. These expenditures are not currently estimable at some sites. NiSource periodically adjusts its accrual as information is collected and estimates become more refined. Air The actions listed below could require further reductions in emissions from various emission sources. NiSource will continue to closely monitor developments in these matters. Climate Change. Future legislative and regulatory programs, including implementation of the EPA CPP, could significantly limit allowed GHG emissions or impose a cost or tax on GHG emissions. Additionally, certain rules that increase methane leak detection and permitting requirements for natural gas facilities could restrict GHG emissions or impose additional costs. The CPP and other federally enacted or proposed GHG reduction measures are subject to numerous legal challenges that could change the way the programs are implemented, and NiSource will carefully monitor all GHG reduction proposals and regulations. In addition to the federal programs, the United States and 194 other countries agreed by consensus to limit GHGs to Nationally Determined Contributions (NDCs) beginning after 2020 in the 2015 United Nations Framework Convention on Climate Change Paris Agreement. The United States has proposed a NDC of a 26-28% reduction from 2005 levels by 2025, a figure that cannot be met with the CPP alone. National Ambient Air Quality Standards. The CAA requires the EPA to set NAAQS for particulate matter and five other pollutants considered harmful to public health and the environment. Periodically, the EPA imposes new, or modifies existing, NAAQS. States that contain areas that do not meet the new or revised standards or contribute significantly to nonattainment of downwind states may be required to take steps to achieve and maintain compliance with the standards. These steps could include additional pollution controls on boilers, engines, turbines and other facilities owned by electric generation and gas distribution operations. The following NAAQS were recently added or modified: Ozone: On October 26, 2015, the EPA issued a final rule to lower the 8-hour ozone standard from 75 ppb to 70 ppb. After the EPA proceeds with designations, areas where NiSource operates that are currently designated in attainment with the standards may be reclassified as nonattainment. NiSource will continue to monitor this matter and cannot estimate its impact at this time. Waste NiSource subsidiaries are potentially responsible parties at waste disposal sites under the CERCLA (commonly known as Superfund) and similar state laws. Additionally, NiSource affiliates have retained environmental liabilities, including cleanup liabilities, associated with certain former operations. A program has been instituted to identify and investigate former MGP sites where Gas Distribution Operations subsidiaries or predecessors may have liability. The program has identified 64 such sites where liability is probable. Remedial actions at many of these sites are being overseen by state or federal environmental agencies through consent agreements or voluntary remediation agreements. NiSource utilizes a probabilistic model to estimate its future remediation costs related to its MGP sites. The model was prepared with the assistance of a third-party and incorporates NiSource and general industry experience with remediating MGP sites. NiSource completes an annual refresh of the model in the second quarter of each fiscal year. No material changes to the estimated future remediation costs were noted as a result of the refresh completed as of June 30, 2015. The total estimated liability at NiSource related to the facilities subject to remediation was $109.7 million and $110.4 million at March 31, 2016 and December 31, 2015, respectively. The liability represents NiSource’s best estimate of the probable cost to remediate the facilities. NiSource believes that it is reasonably possible that remediation costs could vary by as much as $25 million in addition to the costs noted above. Remediation costs are estimated based on the best available information, applicable remediation standards at the balance sheet date and experience with similar facilities. Additional Issues Related to Individual Business Segments The sections below describe various regulatory actions that affect individual business segments for which NiSource has retained a liability. Electric Operations. Air NIPSCO is subject to a number of air-quality mandates in the next several years. The mandates, which include the NSR Consent Decree, the Utility Mercury and Air Toxics Standards Rule (MATS) and the CPP, require or may require NIPSCO to make capital improvements to its electric generating stations. The cost of capital improvements associated with the NSR Consent Decree and MATS is estimated to be $860 million, of which approximately $27.2 million remains to be spent. The cost to comply with the CPP cannot be estimated at this time. Costs incurred for NSR Consent Decree and MATS compliance are currently being recovered through rates. NIPSCO believes that the costs associated with CPP compliance will be eligible for recovery through rates. Utility Mercury and Air Toxics Standards Rule: On February 16, 2012, the EPA issued the MATS rule establishing new emissions limits for mercury and other air toxics. Certain affected NIPSCO units have completed projects to meet the April 2015 compliance deadline. For NIPSCO’s remaining affected units, a one-year compliance extension granted by IDEM delayed the compliance date until April 2016. On June 29, 2015, the United States Supreme Court remanded the MATS rule back to the United States Court of Appeals for the District of Columbia Circuit for further proceedings. On December 15, 2015, the United States Court of Appeals for the District of Columbia Circuit issued an order remanding the MATS rule to the EPA without vacating the rule. The MATS rule remains in effect while the EPA addresses the issues raised by the United State Supreme Court. The EPA indicates that these issues will be fully addressed in 2016. NIPSCO will continue to monitor developments in this matter. NIPSCO completed an IURC-approved plan for the installation of environmental controls needed to comply with the MATS extension. Clean Power Plan: On October 23, 2015, the EPA issued a final rule to regulate CO₂ emissions from existing fossil-fuel EGUs under section 111(d) of the CAA. The final rule establishes national CO₂ emission-rate standards that are applied to each state’s mix of affected EGUs to establish state-specific emission-rate and mass-emission limits. The final rule requires each state to submit a plan indicating how the state will meet the EPA's emission-rate or mass-emission limit, including possibly imposing reduction obligations on specific units. If a state does not submit a satisfactory plan, the EPA will impose a federal plan on that state. On February 9, 2016, the U.S. Supreme Court stayed implementation of the CPP until litigation is decided on its merits. The cost to comply with this rule will depend on a number of factors, including the outcome of CPP litigation, the requirements of the state plan or final federal plan, and the level of NIPSCO's required CO₂ emission reductions. It is possible that this new rule, comprehensive federal or state GHG legislation or other GHG regulation could result in additional expense or compliance costs that could materially impact NiSource's financial results. NIPSCO will continue to monitor this matter and cannot estimate its impact at this time. Cross State Air Pollution Rule: On December 3, 2015, the EPA issued a proposed rule to address interstate air quality impacts associated with the 2008 ozone NAAQS. Under the proposed rule, NIPSCO would be required to meet a more stringent NOx emission allocation. NIPSCO will continue to monitor this matter and cannot estimate its impact at this time. Water On August 15, 2014, the EPA issued the final Phase II Rule of the Clean Water Act Section 316(b), which requires all large existing steam electric generating stations to meet certain performance standards to reduce the effects on aquatic organisms at their cooling water intake structures. Under this rule, stations will have to either demonstrate that the performance of their existing fish protection systems meet the new standards or develop new systems, such as a closed-cycle cooling tower. The cost to comply will depend on a number of factors, including evaluation of the various compliance options available under the regulation and permitting-related determinations by IDEM. NIPSCO estimates that the cost of compliance is between $4 million and $35 million, dependent upon study results, agency requirements and technology ultimately required to achieve compliance. On November 3, 2015, the EPA issued a final rule to amend the ELG and standards for the Steam Electric Power Generating category. The final rule became effective January 4, 2016. The rule imposes new water treatment and discharge requirements on NIPSCO's electric generating facilities to be applied between 2018-2023. Based upon a preliminary engineering study, capital compliance costs are currently expected to be in the $225 million to $315 million range. NIPSCO believes that the costs associated with ELG compliance will be eligible for recovery through rates. Waste On April 17, 2015, the EPA issued a final rule for regulation of CCRs. The rule regulates CCRs under the Resource Conservation and Recovery Act Subtitle D, which determines them to be nonhazardous. The rule will require increased groundwater monitoring, reporting, record keeping and posting of related information to the Internet. The rule also establishes requirements related to CCR management, impoundments, landfills and storage. The rule will allow NIPSCO to continue its byproduct beneficial use program. The publication of the CCR rule resulted in revisions to previously recorded legal obligations associated with the retirement of certain NIPSCO facilities. The actual asset retirement costs related to the CCR rule may vary substantially from the estimates used to record the increased asset retirement obligation due to the uncertainty about the compliance strategies that will be used and the preliminary nature of available data used to estimate costs. Refer to Note 6, "Asset Retirement Obligations," for further information. In addition, to comply with the rule, NIPSCO will be required to incur future capital expenditures to modify its infrastructure and manage CCRs. Based upon a preliminary engineering study, capital compliance costs are currently expected to be in the $130 million to $182 million range. As allowed by the EPA, NIPSCO will continue to collect data over time to determine the specific compliance solutions and associated costs and, as a result, the actual costs may vary. NIPSCO believes that the costs associated with CCR compliance will be eligible for recovery through rates. D. Other Matters. Transmission Upgrade Agreements. On February 11, 2014, NIPSCO entered into TUAs with upgrade sponsors to complete upgrades on NIPSCO’s transmission system on behalf of those sponsors. The upgrade sponsors agreed to reimburse NIPSCO for the total cost to construct transmission upgrades and place them into service, multiplied by a rate of 1.71 ("the multiplier"). On June 10, 2014, certain upgrade sponsors for both TUAs filed a complaint at the FERC against NIPSCO regarding the multiplier stated in the TUAs. On June 30, 2014, NIPSCO filed an answer defending the terms of the TUAs and the just and reasonable nature of the multiplier charged therein and moved for dismissal of the complaint. On December 8, 2014, the FERC issued an order in response to the complaint finding that it is appropriate for NIPSCO to recover, through the multiplier, substantiated costs of ownership related to the TUAs. The FERC set for hearing the issue of what constitutes the incremental costs NIPSCO will incur, but is holding that hearing in abeyance to allow for settlement. NIPSCO will continue to monitor developments in this matter and does not believe the conclusion of this matter will result in a material impact to the Condensed Consolidated Financial Statements (unaudited).

Other Commitments and Contingencies

A. Guarantees and Indemnities. As a part of normal business, NiSource and certain subsidiaries enter into various agreements providing financial or performance assurance to third parties on behalf of certain subsidiaries. Such agreements include guarantees and stand-by letters of credit. These agreements are entered into primarily to support or enhance the creditworthiness otherwise attributed to a subsidiary on a stand-alone basis, thereby facilitating the extension of sufficient credit to accomplish the subsidiaries’ intended commercial purposes. At March 31, 2016, NiSource had issued stand-by letters of credit of approximately $14.7 million for the benefit of third parties.

B. Legal Proceedings. The Company is party to certain claims and legal proceedings arising in the ordinary course of business, none of which is deemed to be individually material at this time. Due to the inherent uncertainty of litigation, there can be no assurance that the resolution of any particular claim or proceeding would not have a material adverse effect on the Company’s results of operations, financial position or liquidity. If one or more of such matters were decided against the Company, the effects could be material to the Company’s results of operations in the period in which the Company would be required to record or adjust the related liability and could also be material to the Company’s cash flows in the periods the Company would be required to pay such liability.

C. Environmental Matters. NiSource operations are subject to environmental statutes and regulations related to air quality, water quality, hazardous waste and solid waste. NiSource believes that it is in substantial compliance with the environmental regulations currently applicable to its operations.

It is management's continued intent to address environmental issues in cooperation with regulatory authorities in such a manner as to achieve mutually acceptable compliance plans. However, there can be no assurance that fines and penalties will not be incurred. Management expects a significant portion of environmental assessment and remediation costs to be recoverable through rates for certain NiSource companies.

As of March 31, 2016 and December 31, 2015, NiSource had recorded an accrual of approximately $122.0 million and $123.2 million, respectively, to cover environmental remediation at various sites. The current portion of this accrual is included in "Legal and environmental" in the Condensed Consolidated Balance Sheets (unaudited). The noncurrent portion is included in "Other noncurrent liabilities" in the Condensed Consolidated Balance Sheets (unaudited). NiSource accrues for costs associated with environmental remediation obligations when the incurrence of such costs is probable and the amounts can be reasonably estimated. The original estimates for cleanup may differ materially from the amount ultimately expended. The actual future expenditures depend on many factors, including currently enacted laws and regulations, the nature and extent of contamination, the method of cleanup and the availability of cost recovery. These expenditures are not currently estimable at some sites. NiSource periodically adjusts its accrual as information is collected and estimates become more refined.

Air

The actions listed below could require further reductions in emissions from various emission sources. NiSource will continue to closely monitor developments in these matters.

Climate Change. Future legislative and regulatory programs, including implementation of the EPA CPP, could significantly limit allowed GHG emissions or impose a cost or tax on GHG emissions. Additionally, certain rules that increase methane leak detection and permitting requirements for natural gas facilities could restrict GHG emissions or impose additional costs. The CPP and other federally enacted or proposed GHG reduction measures are subject to numerous legal challenges that could change the way the programs are implemented, and NiSource will carefully monitor all GHG reduction proposals and regulations. In addition to the federal programs, the United States and 194 other countries agreed by consensus to limit GHGs to Nationally Determined Contributions (NDCs) beginning after 2020 in the 2015 United Nations Framework Convention on Climate Change Paris Agreement. The United States has proposed a NDC of a 26-28% reduction from 2005 levels by 2025, a figure that cannot be met with the CPP alone.

National Ambient Air Quality Standards. The CAA requires the EPA to set NAAQS for particulate matter and five other pollutants considered harmful to public health and the environment. Periodically, the EPA imposes new, or modifies existing, NAAQS. States that contain areas that do not meet the new or revised standards or contribute significantly to nonattainment of downwind states may be required to take steps to achieve and maintain compliance with the standards. These steps could include additional pollution controls on boilers, engines, turbines and other facilities owned by electric generation and gas distribution operations.

The following NAAQS were recently added or modified:

Ozone: On October 26, 2015, the EPA issued a final rule to lower the 8-hour ozone standard from 75 ppb to 70 ppb. After the EPA proceeds with designations, areas where NiSource operates that are currently designated in attainment with the standards may be reclassified as nonattainment. NiSource will continue to monitor this matter and cannot estimate its impact at this time.

Waste

NiSource subsidiaries are potentially responsible parties at waste disposal sites under the CERCLA (commonly known as Superfund) and similar state laws. Additionally, NiSource affiliates have retained environmental liabilities, including cleanup liabilities, associated with certain former operations.

A program has been instituted to identify and investigate former MGP sites where Gas Distribution Operations subsidiaries or predecessors may have liability. The program has identified 64 such sites where liability is probable. Remedial actions at many of these sites are being overseen by state or federal environmental agencies through consent agreements or voluntary remediation agreements.

NiSource utilizes a probabilistic model to estimate its future remediation costs related to its MGP sites. The model was prepared with the assistance of a third-party and incorporates NiSource and general industry experience with remediating MGP sites. NiSource completes an annual refresh of the model in the second quarter of each fiscal year. No material changes to the estimated future remediation costs were noted as a result of the refresh completed as of June 30, 2015. The total estimated liability at NiSource related to the facilities subject to remediation was $109.7 million and $110.4 million at March 31, 2016 and December 31, 2015, respectively. The liability represents NiSource’s best estimate of the probable cost to remediate the facilities. NiSource believes that it is reasonably possible that remediation costs could vary by as much as $25 million in addition to the costs noted above. Remediation costs are estimated based on the best available information, applicable remediation standards at the balance sheet date and experience with similar facilities.

Additional Issues Related to Individual Business Segments

The sections below describe various regulatory actions that affect individual business segments for which NiSource has retained a liability.

Electric Operations.

Air

NIPSCO is subject to a number of air-quality mandates in the next several years. The mandates, which include the NSR Consent Decree, the Utility Mercury and Air Toxics Standards Rule (MATS) and the CPP, require or may require NIPSCO to make capital improvements to its electric generating stations. The cost of capital improvements associated with the NSR Consent Decree and MATS is estimated to be $860 million, of which approximately $27.2 million remains to be spent. The cost to comply with the CPP cannot be estimated at this time. Costs incurred for NSR Consent Decree and MATS compliance are currently being recovered through rates. NIPSCO believes that the costs associated with CPP compliance will be eligible for recovery through rates.

Utility Mercury and Air Toxics Standards Rule: On February 16, 2012, the EPA issued the MATS rule establishing new emissions limits for mercury and other air toxics. Certain affected NIPSCO units have completed projects to meet the April 2015 compliance deadline. For NIPSCO’s remaining affected units, a one-year compliance extension granted by IDEM delayed the compliance date until April 2016. On June 29, 2015, the United States Supreme Court remanded the MATS rule back to the United States Court of Appeals for the District of Columbia Circuit for further proceedings. On December 15, 2015, the United States Court of Appeals for the District of Columbia Circuit issued an order remanding the MATS rule to the EPA without vacating the rule. The MATS rule remains in effect while the EPA addresses the issues raised by the United State Supreme Court. The EPA indicates that these issues will be fully addressed in 2016. NIPSCO will continue to monitor developments in this matter. NIPSCO completed an IURC-approved plan for the installation of environmental controls needed to comply with the MATS extension.

Clean Power Plan: On October 23, 2015, the EPA issued a final rule to regulate CO₂ emissions from existing fossil-fuel EGUs under section 111(d) of the CAA. The final rule establishes national CO₂ emission-rate standards that are applied to each state’s mix of affected EGUs to establish state-specific emission-rate and mass-emission limits. The final rule requires each state to submit a plan indicating how the state will meet the EPA's emission-rate or mass-emission limit, including possibly imposing reduction obligations on specific units. If a state does not submit a satisfactory plan, the EPA will impose a federal plan on that state. On February 9, 2016, the U.S. Supreme Court stayed implementation of the CPP until litigation is decided on its merits. The cost to comply with this rule will depend on a number of factors, including the outcome of CPP litigation, the requirements of the state plan or final federal plan, and the level of NIPSCO's required CO₂ emission reductions. It is possible that this new rule, comprehensive federal or state GHG legislation or other GHG regulation could result in additional expense or compliance costs that could materially impact NiSource's financial results. NIPSCO will continue to monitor this matter and cannot estimate its impact at this time.

Cross State Air Pollution Rule: On December 3, 2015, the EPA issued a proposed rule to address interstate air quality impacts associated with the 2008 ozone NAAQS. Under the proposed rule, NIPSCO would be required to meet a more stringent NOx emission allocation. NIPSCO will continue to monitor this matter and cannot estimate its impact at this time.

Water

On August 15, 2014, the EPA issued the final Phase II Rule of the Clean Water Act Section 316(b), which requires all large existing steam electric generating stations to meet certain performance standards to reduce the effects on aquatic organisms at their cooling water intake structures. Under this rule, stations will have to either demonstrate that the performance of their existing fish protection systems meet the new standards or develop new systems, such as a closed-cycle cooling tower. The cost to comply will depend on a number of factors, including evaluation of the various compliance options available under the regulation and permitting-related determinations by IDEM. NIPSCO estimates that the cost of compliance is between $4 million and $35 million, dependent upon study results, agency requirements and technology ultimately required to achieve compliance.

On November 3, 2015, the EPA issued a final rule to amend the ELG and standards for the Steam Electric Power Generating category. The final rule became effective January 4, 2016. The rule imposes new water treatment and discharge requirements on NIPSCO's electric generating facilities to be applied between 2018-2023. Based upon a preliminary engineering study, capital compliance costs are currently expected to be in the $225 million to $315 million range. NIPSCO believes that the costs associated with ELG compliance will be eligible for recovery through rates.

Waste

On April 17, 2015, the EPA issued a final rule for regulation of CCRs. The rule regulates CCRs under the Resource Conservation and Recovery Act Subtitle D, which determines them to be nonhazardous. The rule will require increased groundwater monitoring, reporting, record keeping and posting of related information to the Internet. The rule also establishes requirements related to CCR management, impoundments, landfills and storage. The rule will allow NIPSCO to continue its byproduct beneficial use program.

The publication of the CCR rule resulted in revisions to previously recorded legal obligations associated with the retirement of certain NIPSCO facilities. The actual asset retirement costs related to the CCR rule may vary substantially from the estimates used to record the increased asset retirement obligation due to the uncertainty about the compliance strategies that will be used and the preliminary nature of available data used to estimate costs. Refer to Note 6, "Asset Retirement Obligations," for further information. In addition, to comply with the rule, NIPSCO will be required to incur future capital expenditures to modify its infrastructure and manage CCRs. Based upon a preliminary engineering study, capital compliance costs are currently expected to be in the $130 million to $182 million range. As allowed by the EPA, NIPSCO will continue to collect data over time to determine the specific compliance solutions and associated costs and, as a result, the actual costs may vary. NIPSCO believes that the costs associated with CCR compliance will be eligible for recovery through rates.

D. Other Matters.

Transmission Upgrade Agreements. On February 11, 2014, NIPSCO entered into TUAs with upgrade sponsors to complete upgrades on NIPSCO’s transmission system on behalf of those sponsors. The upgrade sponsors agreed to reimburse NIPSCO for the total cost to construct transmission upgrades and place them into service, multiplied by a rate of 1.71 ("the multiplier").

On June 10, 2014, certain upgrade sponsors for both TUAs filed a complaint at the FERC against NIPSCO regarding the multiplier stated in the TUAs. On June 30, 2014, NIPSCO filed an answer defending the terms of the TUAs and the just and reasonable nature of the multiplier charged therein and moved for dismissal of the complaint. On December 8, 2014, the FERC issued an order in response to the complaint finding that it is appropriate for NIPSCO to recover, through the multiplier, substantiated costs of ownership related to the TUAs. The FERC set for hearing the issue of what constitutes the incremental costs NIPSCO will incur, but is holding that hearing in abeyance to allow for settlement. NIPSCO will continue to monitor developments in this matter and does not believe the conclusion of this matter will result in a material impact to the Condensed Consolidated Financial Statements (unaudited).