Transfers Of Financial Assets (Narrative) (Details) (USD $) In Millions, unless otherwise specified			6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014 Columbia Gas Of Ohio Receivables Corporation [Member]	Jun. 30, 2014 Columbia Gas Of Pennsylvania Receivables Corporation [Member]	Jun. 30, 2014 NIPSCO Accounts Receivable Corporation [Member]	Jun. 30, 2014 Maximum [Member] Accounts Receivable Program [Member]	Jun. 30, 2014 Maximum [Member] Columbia Gas Of Ohio Receivables Corporation [Member]	Jun. 30, 2014 Maximum [Member] Columbia Gas Of Pennsylvania Receivables Corporation [Member]	Jun. 30, 2014 Maximum [Member] NIPSCO Accounts Receivable Corporation [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Accounts receivable securitization facility borrowings	$ 300.0	$ 265.1				$ 515.0
Trade receivables, seasonal program maximum							240	75	200
Trade Receivable Agreement Expiration Date			Oct. 17, 2014	Mar. 10, 2015	Aug. 27, 2014
Net receivables transferred	$ 300.0	$ 265.1	$ 150.0	$ 25.0	$ 125.0