Document And Entity Information (USD $)	12 Months Ended
	Dec. 31, 2012	Feb. 12, 2013	Jun. 29, 2012
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	FY
Entity Registrant Name	NISOURCE INC/DE
Entity Central Index Key	0001111711
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 7,017,170,104
Entity Common Stock, Shares Outstanding		311,188,068