v2.4.0.8

Transfers Of Financial Assets (Narrative) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 6 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Jun. 30, 2013 | Jun. 30, 2012 | Jun. 30, 2013 | Jun. 30, 2012 | Dec. 31, 2012 | Jun. 30, 2013 Columbia Gas Of Ohio Receivables Corporation [Member] | Jun. 30, 2013 Columbia Gas Of Pennsylvania Receivables Corporation [Member] | Jun. 30, 2013 NIPSCO Accounts Receivable Corporation [Member] | Jun. 30, 2013 Maximum [Member] Accounts Receivable Program [Member] | Oct. 19, 2012 Maximum [Member] Columbia Gas Of Ohio Receivables Corporation [Member] | Mar. 15, 2010 Maximum [Member] Columbia Gas Of Pennsylvania Receivables Corporation [Member] | Aug. 29, 2012 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 | $ 260.1 |  | $ 260.1 |  | $ 233.3 |  |  |  | $ 515.0 |  |  |
Trade receivables, seasonal program maximum |  |  |  |  |  |  |  |  |  | 240 | 75 | 200
Net receivables transferred | 260.1 |  | 260.1 |  | 233.3 | 125.1 | 10.0 | 125.0 |  |  |  |
Securitization transaction fees | $ 0.6 | $ 0.9 | $ 1.5 | $ 2.0 |  |  |  |  |  |  |  |

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- Definition Securitization transaction fees + References No definition available. + Details
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Namespace Prefix: | ni_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Trade receivables transferred, net + References No definition available. + Details
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Namespace Prefix: | ni_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- 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 FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- 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 -Topic 860 -SubTopic 30 -Section 50 -Paragraph 1A -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=7523297&loc=SL6224234-111729 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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