v2.4.0.8

Transfers Of Financial Assets (Schedule Of Gross And Net Receivables Transferred As Well As Short-Term Borrowings Related To The Securitization Transactions) (Details) (USD $) In Millions, unless otherwise specified | Jun. 30, 2013 | Dec. 31, 2012
--- | --- | ---
Gross Receivables interest | $ 455.1 | $ 525.3
Less: Receivables not transferred | 195.0 | 292.0
Net receivables transferred | 260.1 | 233.3
Accounts receivable securitization facility borrowings | $ 260.1 | $ 233.3

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- Definition Trade receivables available for transfer + References No definition available. + Details
Name: | ni_TradeReceivablesAvailableForTransfer
Namespace Prefix: | ni_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Trade receivables not transferred + References No definition available. + Details
Name: | ni_TradeReceivablesNotTransferred
Namespace Prefix: | ni_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Trade receivables transferred, net + References No definition available. + Details
Name: | ni_TradeReceivablesTransferredNet
Namespace Prefix: | ni_
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
Name: | us-gaap_TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant