Gas in Storage	3 Months Ended
Mar. 31, 2017
Gas in Storage [Abstract]
Inventory Disclosure [Text Block]	Gas in Storage Both the LIFO inventory methodology and the weighted-average cost methodology are used by NiSource to value natural gas in storage. Gas Distribution Operations prices natural gas storage injections at the average of the costs of natural gas supply purchased during the year. For interim periods, the difference between current projected replacement cost and the LIFO cost for quantities of gas temporarily withdrawn from storage is recorded as a temporary LIFO liquidation credit or debit within the Condensed Consolidated Balance Sheets (unaudited). Due to seasonality requirements, NiSource expects interim variances in LIFO layers to be replenished by year end. NiSource had a temporary LIFO liquidation debit of $20.6 million and zero as of March 31, 2017 and December 31, 2016, respectively, for certain gas distribution companies recorded within “Prepayments and other,” on the Condensed Consolidated Balance Sheets (unaudited).

Gas in Storage

3 Months Ended

Mar. 31, 2017

Gas in Storage

Both the LIFO inventory methodology and the weighted-average cost methodology are used by NiSource to value natural gas in storage. Gas Distribution Operations prices natural gas storage injections at the average of the costs of natural gas supply purchased during the year. For interim periods, the difference between current projected replacement cost and the LIFO cost for quantities of gas temporarily withdrawn from storage is recorded as a temporary LIFO liquidation credit or debit within the Condensed Consolidated Balance Sheets (unaudited). Due to seasonality requirements, NiSource expects interim variances in LIFO layers to be replenished by year end. NiSource had a temporary LIFO liquidation debit of $20.6 million and zero as of March 31, 2017 and December 31, 2016, respectively, for certain gas distribution companies recorded within “Prepayments and other,” on the Condensed Consolidated Balance Sheets (unaudited).