Risk Management Activities Risk Management Activities (Policy)	6 Months Ended
Jun. 30, 2013
Risk Management Activities [Abstract]
Derivatives, Policy	Accounting Policy for Derivative Instruments. The ASC topic on accounting for derivatives and hedging requires an entity to recognize all derivatives as either assets or liabilities on the Condensed Consolidated Balance Sheets (unaudited) at fair value, unless such contracts are exempted, such as normal purchase and normal sale contracts under the provisions of the ASC topic. The accounting for changes in the fair value of a derivative depends on the intended use of the derivative and resulting designation. NiSource uses a variety of derivative instruments (exchange traded futures and options, physical forwards and options, basis contracts, financial commodity swaps, and interest rate swaps) to effectively manage its commodity price risk and interest rate risk exposure. If certain conditions are met, a derivative may be specifically designated as (a) a hedge of the exposure to changes in the fair value of a recognized asset or liability or an unrecognized firm commitment, or (b) a hedge of the exposure to variable cash flows of a forecasted transaction. In order for a derivative contract to be designated as a hedge, the relationship between the hedging instrument and the hedged item or transaction must be highly effective. The effectiveness test is performed at the inception of the hedge and each reporting period thereafter, throughout the period that the hedge is designated. Any amounts determined to be ineffective are recognized currently in earnings. For derivative contracts that qualify for the normal purchase and normal sales exception, a contract’s fair value is not recognized in the Condensed Consolidated Financial Statements (unaudited) until the contract is settled. Unrealized and realized gains and losses are recognized each period as components of AOCI, regulatory assets and liabilities or earnings depending on the designation of the derivative instrument and regulatory accounting treatment. For subsidiaries that utilize derivatives for cash flow hedges, the effective portions of the gains and losses are recorded to AOCI and are recognized in earnings concurrent with the disposition of the hedged risks. If a forecasted transaction corresponding to a cash flow hedge is no longer probable to occur, the accumulated gains or losses on the derivative are recognized currently in earnings. For fair value hedges, the gains and losses are recorded in earnings each period together with the change in the fair value of the hedged item. As a result of the rate-making process, the rate-regulated subsidiaries generally record gains and losses as regulatory liabilities or assets and recognize such gains or losses in earnings when both the contracts settle and the physical commodity flows. These gains and losses recognized in earnings are then subsequently recovered or passed back to customers in revenues through rates. When gains and losses are recognized in earnings, they are recognized in revenues or cost of sales for derivatives that correspond to commodity risk activities and are recognized in interest expense for derivatives that correspond to interest-rate risk activities. For its commodity price risk programs, NiSource has elected not to net the fair value amounts of its derivative instruments or the fair value amounts recognized for its right to receive or obligation to pay cash collateral arising from those derivative instruments recognized at fair value, which are executed with the same counterparty under a master netting arrangement. NiSource discloses amounts recognized for the right to reclaim cash collateral within “Restricted cash” and amounts recognized for the obligation to return cash collateral within “Other accruals” on the Condensed Consolidated Balance Sheets (unaudited).

Accounting Policy for Derivative Instruments. The ASC topic on accounting for derivatives and hedging requires an entity to recognize all derivatives as either assets or liabilities on the Condensed Consolidated Balance Sheets (unaudited) at fair value, unless such contracts are exempted, such as normal purchase and normal sale contracts under the provisions of the ASC topic. The accounting for changes in the fair value of a derivative depends on the intended use of the derivative and resulting designation.

NiSource uses a variety of derivative instruments (exchange traded futures and options, physical forwards and options, basis contracts, financial commodity swaps, and interest rate swaps) to effectively manage its commodity price risk and interest rate risk exposure. If certain conditions are met, a derivative may be specifically designated as (a) a hedge of the exposure to changes in the fair value of a recognized asset or liability or an unrecognized firm commitment, or (b) a hedge of the exposure to variable cash flows of a forecasted transaction. In order for a derivative contract to be designated as a hedge, the relationship between the hedging instrument and the hedged item or transaction must be highly effective. The effectiveness test is performed at the inception of the hedge and each reporting period thereafter, throughout the period that the hedge is designated. Any amounts determined to be ineffective are recognized currently in earnings. For derivative contracts that qualify for the normal purchase and normal sales exception, a contract’s fair value is not recognized in the Condensed Consolidated Financial Statements (unaudited) until the contract is settled.

Unrealized and realized gains and losses are recognized each period as components of AOCI, regulatory assets and liabilities or earnings depending on the designation of the derivative instrument and regulatory accounting treatment. For subsidiaries that utilize derivatives for cash flow hedges, the effective portions of the gains and losses are recorded to AOCI and are recognized in earnings concurrent with the disposition of the hedged risks. If a forecasted transaction corresponding to a cash flow hedge is no longer probable to occur, the accumulated gains or losses on the derivative are recognized currently in earnings. For fair value hedges, the gains and losses are recorded in earnings each period together with the change in the fair value of the hedged item. As a result of the rate-making process, the rate-regulated subsidiaries generally record gains and losses as regulatory liabilities or assets and recognize such gains or losses in earnings when both the contracts settle and the physical commodity flows. These gains and losses recognized in earnings are then subsequently recovered or passed back to customers in revenues through rates. When gains and losses are recognized in earnings, they are recognized in revenues or cost of sales for derivatives that correspond to commodity risk activities and are recognized in interest expense for derivatives that correspond to interest-rate risk activities.

For its commodity price risk programs, NiSource has elected not to net the fair value amounts of its derivative instruments or the fair value amounts recognized for its right to receive or obligation to pay cash collateral arising from those derivative instruments recognized at fair value, which are executed with the same counterparty under a master netting arrangement. NiSource discloses amounts recognized for the right to reclaim cash collateral within “Restricted cash” and amounts recognized for the obligation to return cash collateral within “Other accruals” on the Condensed Consolidated Balance Sheets (unaudited).