Long-Term Debt	6 Months Ended
Jun. 30, 2016
Long-term Debt, Current and Noncurrent [Abstract]
Long-term Debt	Long-Term Debt In June 2016, NiSource Finance entered into forward-starting interest rate swaps with an aggregate notional amount of $500.0 million to hedge the variability in cash flows attributable to changes in the benchmark interest rate during the period from the effective date of the swaps to the anticipated date of forecasted debt issuances, expected to take place by the end of 2018. The forward-starting interest rate swaps were designated as cash flow hedges at the time the agreements were executed, whereby any gain or loss recognized from the effective date of the swaps to the date the associated debt is issued for the effective portion of the hedge is recorded net of tax in AOCI and amortized as a component of interest expense over the life of the designated debt. If some portion of the hedges becomes ineffective, the associated gain or loss will be recognized in earnings. As of June 30, 2016, no ineffectiveness has been recorded. On March 31, 2016, NiSource Finance entered into a $500.0 million term loan agreement with a syndicate of banks. NiSource Finance may borrow up to $500.0 million at any time or from time to time before September 30, 2016. Until September 30, 2016, NiSource Finance will pay a fee of 17.5 basis points on any portion of the $500.0 million commitment that is not borrowed. Any portion of the $500.0 million commitment that is not borrowed at September 30, 2016 will be forfeited. The term loan matures March 29, 2019, at which point any and all outstanding borrowings under the agreement are due. Interest charged on borrowings depends on the variable rate structure elected by NiSource Finance at the time of each borrowing. The available variable rate structures from which NiSource Finance may choose are defined in the term loan agreement. As of June 30, 2016, NiSource had no outstanding borrowings under the term loan agreement. On March 15, 2016, NiSource Finance redeemed $201.5 million of 10.75% senior unsecured notes at maturity.

Long-Term Debt

In June 2016, NiSource Finance entered into forward-starting interest rate swaps with an aggregate notional amount of $500.0 million to hedge the variability in cash flows attributable to changes in the benchmark interest rate during the period from the effective date of the swaps to the anticipated date of forecasted debt issuances, expected to take place by the end of 2018. The forward-starting interest rate swaps were designated as cash flow hedges at the time the agreements were executed, whereby any gain or loss recognized from the effective date of the swaps to the date the associated debt is issued for the effective portion of the hedge is recorded net of tax in AOCI and amortized as a component of interest expense over the life of the designated debt. If some portion of the hedges becomes ineffective, the associated gain or loss will be recognized in earnings. As of June 30, 2016, no ineffectiveness has been recorded.

On March 31, 2016, NiSource Finance entered into a $500.0 million term loan agreement with a syndicate of banks. NiSource Finance may borrow up to $500.0 million at any time or from time to time before September 30, 2016. Until September 30, 2016, NiSource Finance will pay a fee of 17.5 basis points on any portion of the $500.0 million commitment that is not borrowed. Any portion of the $500.0 million commitment that is not borrowed at September 30, 2016 will be forfeited. The term loan matures March 29, 2019, at which point any and all outstanding borrowings under the agreement are due. Interest charged on borrowings depends on the variable rate structure elected by NiSource Finance at the time of each borrowing. The available variable rate structures from which NiSource Finance may choose are defined in the term loan agreement. As of June 30, 2016, NiSource had no outstanding borrowings under the term loan agreement.

On March 15, 2016, NiSource Finance redeemed $201.5 million of 10.75% senior unsecured notes at maturity.