2.2.0.7 true Accounting Policies and Interim Results (Details) (USD $) 0601 - Disclosure - Accounting Policies and Interim Results (Details) true false In Millions false false 1 USD true false false false Successor us-gaap_StatementScenarioAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SuccessorMember us-gaap_StatementScenarioAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 2 USD true false false false Subsequent Event [Member] us-gaap_SubsequentEventTypeAxis xbrldi http://xbrl.org/2006/xbrldi bni_SubsequentEventMember us-gaap_SubsequentEventTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ 4 Business Acquisition [Line Items] 2 us-gaap_BusinessAcquisitionLineItems us-gaap true na duration No definition available. false false false false false true false false false false false false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false xbrli:stringItemType string Line items represent financial concepts included in a table. 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No authoritative reference available. false 9 The unrelated General Partner's ownership percentage of investment in low income housing partnership 3 bni_UnrelatedGeneralPartnersOwnershipPercentageOfInvestmentInLowIncomeHousingPartnership bni false na duration The unrelated General Partner's ownership percentage of investment in low-income housing partnership. false false false false false false false false false false false verboselabel false 1 false false false false 0 0 true false false 2 false true false false 0.001 0.001 true false false us-types:percentItemType pure The unrelated General Partner's ownership percentage of investment in low-income housing partnership. 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No authoritative reference available. false 14 Accounting Policies and Interim Results (Textuals) [Abstract] 3 bni_AccountingPoliciesAndInterimResultsTextualsAbstract bni false na duration Accounting Policies and Interim Results. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 true false false xbrli:stringItemType string Accounting Policies and Interim Results. false 15 Number of fair value hedge separate swap agreements 4 bni_NumberOfFairValueHedgeSeparateSwapAgreements bni false na duration Number of fair value hedge separate swap agreements. false false false false false false false false false false false verboselabel false 1 false false false false 0 0 true false false 2 false true false false 4 4 true false false xbrli:integerItemType integer Number of fair value hedge separate swap agreements. 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No authoritative reference available. false 17 Original swap entrance date 4 bni_OriginalSwapEntranceDate bni false na duration Original swap entrance date. false false false false false false false false false false false verboselabel false 1 false false false false 0 0 true false false 2 false false false false 0 0 March 2008 March 2008 true false false xbrli:stringItemType string Original swap entrance date. No authoritative reference available. false 18 Original fixed rate on 10-year notes 4 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false terselabel false 1 false false false false 0 0 true false false 2 false true false false 0.0575 0.0575 true false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. 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