v2.3.0.11

Transfers of Financial Assets (Narrative) (Details) (USD $) In Millions	3 Months Ended		6 Months Ended								6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010	Oct. 22, 2010 Maximum [Member] Columbia Gas of Ohio Receivables Corporation [Member]	Oct. 23, 2009 Maximum [Member] Columbia Gas of Ohio Receivables Corporation [Member]	Oct. 23, 2009 Maximum [Member] Nipsco Accounts Receivable Corporation [Member]	Mar. 15, 2010 Maximum [Member] Columbia Gas of Pennsylvania Receivables Corporation [Member]	Jun. 30, 2011 Accounts Receivable Program [Member]	Jun. 30, 2011 Columbia Gas of Ohio Receivables Corporation [Member]	Jun. 30, 2011 Nipsco Accounts Receivable Corporation [Member]	Jun. 30, 2011 Columbia Gas of Pennsylvania Receivables Corporation [Member]
Carrying amount of trade receivables transferred											$ 75.0	$ 100.0	$ 8.9
Maximum amount of debt recognized	183.9		183.9		275.0					475.0
Trade receivables, seasonal program maximum						200	275	200	75
Securitization transaction fees	$ 0.8	$ 1.8	$ 2.3	$ 3.7

X

- Definition

The carrying amount of trade receivables transferred.

+ Details

Name:	ni_CarryingAmountOfTradeReceivablesTransferred
Namespace Prefix:	ni
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Securitization transaction fees

+ Details

Name:	ni_SecuritizationTransactionFees
Namespace Prefix:	ni
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

The face amount of accounts receivable that will be sold to other entities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Statement of Position (SOP)
-Number 01-6
-Paragraph 13
-Subparagraph d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6375948&loc=d3e4428-111522

+ Details

Name:	us-gaap_TradeReceivablesHeldForSaleAmount
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Carrying amount of liabilities associated with financial assets accounted for as secured borrowings recognized in the transferor's statement of financial position at the end of each period presented.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)
-SubTopic 30
-Topic 860
-URI http://asc.fasb.org/extlink&oid=6862952&loc=SL6224234-111729

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS140-4/FIN46(R)-8
-Paragraph B12
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant