Income Taxes	9 Months Ended
Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes NiSource’s interim effective tax rates reflect the estimated annual effective tax rates for 2016 and 2015, adjusted for tax expense associated with certain discrete items. The effective tax rates for the three months ended September 30, 2016 and 2015 were 26.4% and 28.2%, respectively. The effective tax rates for the nine months ended September 30, 2016 and 2015 were 35.3% and 35.8%, respectively. These effective tax rates differ from the Federal tax rate of 35% primarily due to the effects of tax credits, state income taxes, utility ratemaking, and other permanent book-to-tax differences. The decrease in the three month effective tax rate of 1.8% in 2016 versus the same period in 2015 is primarily due to favorable estimate-to-actual adjustments related to 2015 tax returns and estimated state apportionment benefits for 2016, partially offset by a 2015 cumulative adjustment to the estimated annual effective tax rate. The decrease in the year-to-date effective tax rate of 0.5% in 2016 versus the same period in 2015 is primarily due to 2016 excess stock compensation benefits from the adoption of ASU 2016-09, offset by differences in state apportionment benefits between 2016 and 2015. Refer to Note 2, "Recent Accounting Pronouncements," for additional information. There were no material changes recorded in 2016 to NiSource's uncertain tax positions as of December 31, 2015.

Income Taxes

9 Months Ended

Sep. 30, 2016

NiSource’s interim effective tax rates reflect the estimated annual effective tax rates for 2016 and 2015, adjusted for tax expense associated with certain discrete items. The effective tax rates for the three months ended September 30, 2016 and 2015 were 26.4% and 28.2%, respectively. The effective tax rates for the nine months ended September 30, 2016 and 2015 were 35.3% and 35.8%, respectively. These effective tax rates differ from the Federal tax rate of 35% primarily due to the effects of tax credits, state income taxes, utility ratemaking, and other permanent book-to-tax differences.

The decrease in the three month effective tax rate of 1.8% in 2016 versus the same period in 2015 is primarily due to favorable estimate-to-actual adjustments related to 2015 tax returns and estimated state apportionment benefits for 2016, partially offset by a 2015 cumulative adjustment to the estimated annual effective tax rate.

The decrease in the year-to-date effective tax rate of 0.5% in 2016 versus the same period in 2015 is primarily due to 2016 excess stock compensation benefits from the adoption of ASU 2016-09, offset by differences in state apportionment benefits between 2016 and 2015. Refer to Note 2, "Recent Accounting Pronouncements," for additional information.

There were no material changes recorded in 2016 to NiSource's uncertain tax positions as of December 31, 2015.