Goodwill	9 Months Ended
Sep. 30, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill NiSource tests its goodwill for impairment annually as of May 1 unless indicators, events, or circumstances would require an immediate review. Goodwill is tested for impairment using financial information at the reporting unit level, which is consistent with the level of discrete financial information reviewed by operating segment management. NiSource's three reporting units are Columbia Distribution Operations, Columbia Transmission Operations and NIPSCO Gas Distribution Operations. NiSource's goodwill assets as of September 30, 2014 were $3.7 billion pertaining primarily to the acquisition of Columbia on November 1, 2000. Of this amount, approximately $2.0 billion is allocated to Columbia Transmission Operations and $1.7 billion is allocated to Columbia Distribution Operations. In addition, NIPSCO Gas Distribution Operations' goodwill assets of $17.8 million at September 30, 2014 relate to the purchase of Northern Indiana Fuel and Light in March 1993 and Kokomo Gas in February 1992. NiSource completed a quantitative ("step 1") fair value measurement of its reporting units during the May 1, 2012 goodwill test. The test indicated that the fair value of each of the reporting units that carry or are allocated goodwill substantially exceeded their carrying values, indicating that no impairment existed. ASU 2011-08 allows entities testing goodwill for impairment the option of performing a qualitative ("step 0") assessment before calculating the fair value of a reporting unit for the goodwill impairment test. If a step 0 assessment is performed, an entity is no longer required to calculate the fair value of a reporting unit unless the entity determines that, based on that assessment, it is more likely than not that its fair value is less than its carrying amount. NiSource applied the qualitative step 0 analysis to its reporting units for the annual impairment test performed as of May 1, 2014. For the current year test, NiSource assessed various assumptions, events and circumstances that would have affected the estimated fair value of the reporting units as compared to its base line May 1, 2012 step 1 fair value measurement. The results of this assessment indicated that it is not more likely than not that its reporting unit fair values are less than the reporting unit carrying values. NiSource considered whether there were any events or changes in circumstances subsequent to the annual test that would reduce the fair value of any of the reporting units below their carrying amounts and necessitate another goodwill impairment test. No such indicators were noted that would require a subsequent goodwill impairment testing during the third quarter.

Goodwill

9 Months Ended

Sep. 30, 2014

Goodwill and Intangible Assets Disclosure [Abstract]

NiSource tests its goodwill for impairment annually as of May 1 unless indicators, events, or circumstances would require an immediate review. Goodwill is tested for impairment using financial information at the reporting unit level, which is consistent with the level of discrete financial information reviewed by operating segment management. NiSource's three reporting units are Columbia Distribution Operations, Columbia Transmission Operations and NIPSCO Gas Distribution Operations.

NiSource's goodwill assets as of September 30, 2014 were $3.7 billion pertaining primarily to the acquisition of Columbia on November 1, 2000. Of this amount, approximately $2.0 billion is allocated to Columbia Transmission Operations and $1.7 billion is allocated to Columbia Distribution Operations. In addition, NIPSCO Gas Distribution Operations' goodwill assets of $17.8 million at September 30, 2014 relate to the purchase of Northern Indiana Fuel and Light in March 1993 and Kokomo Gas in February 1992.

NiSource completed a quantitative ("step 1") fair value measurement of its reporting units during the May 1, 2012 goodwill test. The test indicated that the fair value of each of the reporting units that carry or are allocated goodwill substantially exceeded their carrying values, indicating that no impairment existed.

ASU 2011-08 allows entities testing goodwill for impairment the option of performing a qualitative ("step 0") assessment before calculating the fair value of a reporting unit for the goodwill impairment test. If a step 0 assessment is performed, an entity is no longer required to calculate the fair value of a reporting unit unless the entity determines that, based on that assessment, it is more likely than not that its fair value is less than its carrying amount.

NiSource applied the qualitative step 0 analysis to its reporting units for the annual impairment test performed as of May 1, 2014. For the current year test, NiSource assessed various assumptions, events and circumstances that would have affected the estimated fair value of the reporting units as compared to its base line May 1, 2012 step 1 fair value measurement. The results of this assessment indicated that it is not more likely than not that its reporting unit fair values are less than the reporting unit carrying values.

NiSource considered whether there were any events or changes in circumstances subsequent to the annual test that would reduce the fair value of any of the reporting units below their carrying amounts and necessitate another goodwill impairment test. No such indicators were noted that would require a subsequent goodwill impairment testing during the third quarter.