Income Taxes	6 Months Ended
Jun. 30, 2013
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes NiSource’s interim effective tax rates reflect the estimated annual effective tax rates for 2013 and 2012, adjusted for tax expense associated with certain discrete items. The effective tax rates for the three months ended June 30, 2013 and 2012 were 31.2% and 34.7%, respectively. The effective tax rates for the six months ended June 30, 2013 and 2012 were 34.4% and 34.7%, 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 rate-making, and other permanent book-to-tax differences. The decrease in the three month effective tax rate of 3.5% in 2013 versus 2012 is due primarily to net state deferred income taxes that were remeasured for changes in future apportioned taxable income. This resulted in a net state income tax benefit of $3.3 million. On January 2, 2013, the President signed into law the American Taxpayer Relief Act of 2012 (ATRA). ATRA, among other things, extends retroactively the research credit under Internal Revenue Code section 41 until December 31, 2013, and also extends and modifies 50% bonus depreciation for 2013. In general, 50% bonus depreciation will be available for property placed in service before January 1, 2014, or in the case of certain property having longer production periods, before January 1, 2015. NiSource recorded the effects of ATRA in the first quarter 2013. The retroactive extension of the research credit did not have a significant effect on net income. On March 7, 2013, the congressional Joint Committee on Taxation took no exception to the conclusions reached by the IRS in its 2008-2010 audit examination of NiSource. Therefore, in the first quarter of 2013, NiSource recognized a federal income tax receivable of $15.9 million that was related to the 2008 and 2009 tax years and increases in net operating loss carryforwards of $0.6 million that was related to uncertain tax positions in the 2010-2012 tax years. NiSource received payments of $75.1 million in March 2013 and $70.6 million in April 2013 of principal and interest from the IRS related to the audit examination. The recognition of the receivables and net operating loss carryforwards did not materially affect tax expense or net income. There were no material changes recorded in the second quarter of 2013 to NiSource's uncertain tax positions as of December 31, 2012.

Income Taxes

NiSource’s interim effective tax rates reflect the estimated annual effective tax rates for 2013 and 2012, adjusted for tax expense associated with certain discrete items. The effective tax rates for the three months ended June 30, 2013 and 2012 were 31.2% and 34.7%, respectively. The effective tax rates for the six months ended June 30, 2013 and 2012 were 34.4% and 34.7%, 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 rate-making, and other permanent book-to-tax differences.

The decrease in the three month effective tax rate of 3.5% in 2013 versus 2012 is due primarily to net state deferred income taxes that were remeasured for changes in future apportioned taxable income. This resulted in a net state income tax benefit of $3.3 million.

On January 2, 2013, the President signed into law the American Taxpayer Relief Act of 2012 (ATRA). ATRA, among other things, extends retroactively the research credit under Internal Revenue Code section 41 until December 31, 2013, and also extends and modifies 50% bonus depreciation for 2013. In general, 50% bonus depreciation will be available for property placed in service before January 1, 2014, or in the case of certain property having longer production periods, before January 1, 2015. NiSource recorded the effects of ATRA in the first quarter 2013. The retroactive extension of the research credit did not have a significant effect on net income.

On March 7, 2013, the congressional Joint Committee on Taxation took no exception to the conclusions reached by the IRS in its 2008-2010 audit examination of NiSource. Therefore, in the first quarter of 2013, NiSource recognized a federal income tax receivable of $15.9 million that was related to the 2008 and 2009 tax years and increases in net operating loss carryforwards of $0.6 million that was related to uncertain tax positions in the 2010-2012 tax years. NiSource received payments of $75.1 million in March 2013 and $70.6 million in April 2013 of principal and interest from the IRS related to the audit examination. The recognition of the receivables and net operating loss carryforwards did not materially affect tax expense or net income.

There were no material changes recorded in the second quarter of 2013 to NiSource's uncertain tax positions as of December 31, 2012.