2.4.0.8040020 - Disclosure - Mortgage-Backed Securities - By Type (Details)truefalsefalse1false USDfalsefalse$AS_OF_Jun30_2013http://www.sec.gov/CIK0001275477instant2013-06-30T00:00:000001-01-01T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$2false USDfalsefalse$AS_OF_Dec31_2012http://www.sec.gov/CIK0001275477instant2012-12-31T00:00:000001-01-01T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$1true 3bmnm_MortgageBackedSecuritiesLineItemsbmnm_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Mortgage Backed Securities [Line Items]2false 4bmnm_MortgageBackedSecuritiesAtFairValuebmnm_falsedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse380559808380559808USD$falsetruefalse2truefalsefalse168155007168155007USD$falsetruefalsexbrli:monetaryItemTypemonetaryInvestments in mortgage backed securities which are accounted for under the Fair Value Option. Such securities are reported at fair value; gains (losses) are included in earnings.No definition available.false2Fair Value3false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3false USDtruefalse$AS_OF_Jun30_2013_us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis_VariableInterestEntityPrimaryBeneficiaryMemberhttp://www.sec.gov/CIK0001275477instant2013-06-30T00:00:000001-01-01T00:00:00falsefalse[VariableInterestEntityPrimaryBeneficiaryMember]us-gaap_VariableInterestEntitiesByClassificationOfEntityAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_VariableInterestEntityPrimaryBeneficiaryMemberus-gaap_VariableInterestEntitiesByClassificationOfEntityAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0[VariableInterestEntityPrimaryBeneficiaryMember]4true 3bmnm_MortgageBackedSecuritiesLineItemsbmnm_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Mortgage Backed Securities [Line Items]5false 4bmnm_MortgageBackedSecuritiesAtFairValuebmnm_falsedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse339147913339147913USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryInvestments in mortgage backed securities which are accounted for under the Fair Value Option. Such securities are reported at fair value; gains (losses) are included in earnings.No definition available.false2Fair Value6false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse5false USDtruefalse$AS_OF_Jun30_2013_bmnm_MajorCategoriesOfMortgageBackedSecuritiesAxis_MortgageBackedSecuritiesPassThroughCertificatesMemberhttp://www.sec.gov/CIK0001275477instant2013-06-30T00:00:000001-01-01T00:00:00falsefalse[MortgageBackedSecuritiesPassThroughCertificatesMember]bmnm_MajorCategoriesOfMortgageBackedSecuritiesAxisxbrldihttp://xbrl.org/2006/xbrldibmnm_MortgageBackedSecuritiesPassThroughCertificatesMemberbmnm_MajorCategoriesOfMortgageBackedSecuritiesAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0[MortgageBackedSecuritiesPassThroughCertificatesMember]7true 3bmnm_MortgageBackedSecuritiesLineItemsbmnm_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Mortgage Backed Securities [Line Items]8false 4bmnm_MortgageBackedSecuritiesAtFairValuebmnm_falsedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse356071000356071000USD$falsefalsefalse2truefalsefalse158396000158396000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryInvestments in mortgage backed securities which are accounted for under the Fair Value Option. Such securities are reported at fair value; gains (losses) are included in earnings.No definition available.false2Fair Value9false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse7false USDtruefalse$AS_OF_Jun30_2013_bmnm_MajorCategoriesOfMortgageBackedSecuritiesAxis_MortgageBackedSecuritiesStructuredCertificatesMemberhttp://www.sec.gov/CIK0001275477instant2013-06-30T00:00:000001-01-01T00:00:00falsefalse[MortgageBackedSecuritiesStructuredCertificatesMember]bmnm_MajorCategoriesOfMortgageBackedSecuritiesAxisxbrldihttp://xbrl.org/2006/xbrldibmnm_MortgageBackedSecuritiesStructuredCertificatesMemberbmnm_MajorCategoriesOfMortgageBackedSecuritiesAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0[MortgageBackedSecuritiesStructuredCertificatesMember]10true 3bmnm_MortgageBackedSecuritiesLineItemsbmnm_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Mortgage Backed Securities [Line Items]11false 4bmnm_MortgageBackedSecuritiesAtFairValuebmnm_falsedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse2448900024489000USD$falsefalsefalse2truefalsefalse97590009759000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryInvestments in mortgage backed securities which are accounted for under the Fair Value Option. Such securities are reported at fair value; gains (losses) are included in earnings.No definition available.false2Fair Value12false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse9false USDtruefalse$AS_OF_Jun30_2013_bmnm_MajorCategoriesOfMortgageBackedSecuritiesAxis_MortgageBackedSecuritiesPassThroughCertificatesMember_bmnm_MajorTypesOfMortgageBackedSecuritiesAxis_HybridAdjustableRateMortgagesMemberhttp://www.sec.gov/CIK0001275477instant2013-06-30T00:00:000001-01-01T00:00:00falsefalse[HybridAdjustableRateMortgagesMember]bmnm_MajorTypesOfMortgageBackedSecuritiesAxisxbrldihttp://xbrl.org/2006/xbrldibmnm_HybridAdjustableRateMortgagesMemberbmnm_MajorTypesOfMortgageBackedSecuritiesAxisexplicitMemberfalsefalse[MortgageBackedSecuritiesPassThroughCertificatesMember]bmnm_MajorCategoriesOfMortgageBackedSecuritiesAxisxbrldihttp://xbrl.org/2006/xbrldibmnm_MortgageBackedSecuritiesPassThroughCertificatesMemberbmnm_MajorCategoriesOfMortgageBackedSecuritiesAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0[HybridAdjustableRateMortgagesMember] | [MortgageBackedSecuritiesPassThroughCertificatesMember]13true 3bmnm_MortgageBackedSecuritiesLineItemsbmnm_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Mortgage Backed Securities [Line Items]14false 4bmnm_MortgageBackedSecuritiesAtFairValuebmnm_falsedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse116618000116618000USD$falsefalsefalse2truefalsefalse8769300087693000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryInvestments in mortgage backed securities which are accounted for under the Fair Value Option. Such securities are reported at fair value; gains (losses) are included in earnings.No definition available.false2Fair Value15false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse11false USDtruefalse$AS_OF_Jun30_2013_bmnm_MajorCategoriesOfMortgageBackedSecuritiesAxis_MortgageBackedSecuritiesPassThroughCertificatesMember_bmnm_MajorTypesOfMortgageBackedSecuritiesAxis_AdjustableRateMortgagesMemberhttp://www.sec.gov/CIK0001275477instant2013-06-30T00:00:000001-01-01T00:00:00falsefalse[AdjustableRateMortgagesMember]bmnm_MajorTypesOfMortgageBackedSecuritiesAxisxbrldihttp://xbrl.org/2006/xbrldibmnm_AdjustableRateMortgagesMemberbmnm_MajorTypesOfMortgageBackedSecuritiesAxisexplicitMemberfalsefalse[MortgageBackedSecuritiesPassThroughCertificatesMember]bmnm_MajorCategoriesOfMortgageBackedSecuritiesAxisxbrldihttp://xbrl.org/2006/xbrldibmnm_MortgageBackedSecuritiesPassThroughCertificatesMemberbmnm_MajorCategoriesOfMortgageBackedSecuritiesAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0[AdjustableRateMortgagesMember] | [MortgageBackedSecuritiesPassThroughCertificatesMember]16true 3bmnm_MortgageBackedSecuritiesLineItemsbmnm_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Mortgage Backed Securities [Line Items]17false 4bmnm_MortgageBackedSecuritiesAtFairValuebmnm_falsedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse62100006210000USD$falsefalsefalse2truefalsefalse2085700020857000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryInvestments in mortgage backed securities which are accounted for under the Fair Value Option. Such securities are reported at fair value; gains (losses) are included in earnings.No definition available.false2Fair Value18false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse13false USDtruefalse$AS_OF_Jun30_2013_bmnm_MajorCategoriesOfMortgageBackedSecuritiesAxis_MortgageBackedSecuritiesPassThroughCertificatesMember_bmnm_MajorTypesOfMortgageBackedSecuritiesAxis_FixedRateMortgagesMemberhttp://www.sec.gov/CIK0001275477instant2013-06-30T00:00:000001-01-01T00:00:00falsefalse[FixedRateMortgagesMember]bmnm_MajorTypesOfMortgageBackedSecuritiesAxisxbrldihttp://xbrl.org/2006/xbrldibmnm_FixedRateMortgagesMemberbmnm_MajorTypesOfMortgageBackedSecuritiesAxisexplicitMemberfalsefalse[MortgageBackedSecuritiesPassThroughCertificatesMember]bmnm_MajorCategoriesOfMortgageBackedSecuritiesAxisxbrldihttp://xbrl.org/2006/xbrldibmnm_MortgageBackedSecuritiesPassThroughCertificatesMemberbmnm_MajorCategoriesOfMortgageBackedSecuritiesAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0[FixedRateMortgagesMember] | [MortgageBackedSecuritiesPassThroughCertificatesMember]19true 3bmnm_MortgageBackedSecuritiesLineItemsbmnm_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Mortgage Backed Securities [Line Items]20false 4bmnm_MortgageBackedSecuritiesAtFairValuebmnm_falsedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse233243000233243000USD$falsefalsefalse2truefalsefalse4984600049846000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryInvestments in mortgage backed securities which are accounted for under the Fair Value Option. Such securities are reported at fair value; gains (losses) are included in earnings.No definition available.false2Fair Value21false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse15false USDtruefalse$AS_OF_Jun30_2013_bmnm_MajorCategoriesOfMortgageBackedSecuritiesAxis_MortgageBackedSecuritiesStructuredCertificatesMember_bmnm_MajorTypesOfMortgageBackedSecuritiesAxis_InterestOnlySecuritiesMemberhttp://www.sec.gov/CIK0001275477instant2013-06-30T00:00:000001-01-01T00:00:00falsefalse[InterestOnlySecuritiesMember]bmnm_MajorTypesOfMortgageBackedSecuritiesAxisxbrldihttp://xbrl.org/2006/xbrldibmnm_InterestOnlySecuritiesMemberbmnm_MajorTypesOfMortgageBackedSecuritiesAxisexplicitMemberfalsefalse[MortgageBackedSecuritiesStructuredCertificatesMember]bmnm_MajorCategoriesOfMortgageBackedSecuritiesAxisxbrldihttp://xbrl.org/2006/xbrldibmnm_MortgageBackedSecuritiesStructuredCertificatesMemberbmnm_MajorCategoriesOfMortgageBackedSecuritiesAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0[InterestOnlySecuritiesMember] | [MortgageBackedSecuritiesStructuredCertificatesMember]22true 3bmnm_MortgageBackedSecuritiesLineItemsbmnm_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Mortgage Backed Securities [Line Items]23false 4bmnm_MortgageBackedSecuritiesAtFairValuebmnm_falsedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse2190700021907000USD$falsefalsefalse2truefalsefalse52440005244000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryInvestments in mortgage backed securities which are accounted for under the Fair Value Option. Such securities are reported at fair value; gains (losses) are included in earnings.No definition available.false2Fair Value24false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse17false USDtruefalse$AS_OF_Jun30_2013_bmnm_MajorCategoriesOfMortgageBackedSecuritiesAxis_MortgageBackedSecuritiesStructuredCertificatesMember_bmnm_MajorTypesOfMortgageBackedSecuritiesAxis_InverseInterestOnlyMemberhttp://www.sec.gov/CIK0001275477instant2013-06-30T00:00:000001-01-01T00:00:00falsefalse[InverseInterestOnlyMember]bmnm_MajorTypesOfMortgageBackedSecuritiesAxisxbrldihttp://xbrl.org/2006/xbrldibmnm_InverseInterestOnlyMemberbmnm_MajorTypesOfMortgageBackedSecuritiesAxisexplicitMemberfalsefalse[MortgageBackedSecuritiesStructuredCertificatesMember]bmnm_MajorCategoriesOfMortgageBackedSecuritiesAxisxbrldihttp://xbrl.org/2006/xbrldibmnm_MortgageBackedSecuritiesStructuredCertificatesMemberbmnm_MajorCategoriesOfMortgageBackedSecuritiesAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0[InverseInterestOnlyMember] | [MortgageBackedSecuritiesStructuredCertificatesMember]25true 3bmnm_MortgageBackedSecuritiesLineItemsbmnm_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Mortgage Backed Securities [Line Items]26false 4bmnm_MortgageBackedSecuritiesAtFairValuebmnm_falsedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse25820002582000USD$falsetruefalse2truefalsefalse45150004515000USD$falsetruefalsexbrli:monetaryItemTypemonetaryInvestments in mortgage backed securities which are accounted for under the Fair Value Option. Such securities are reported at fair value; gains (losses) are included in earnings.No definition available.false2Fair ValuefalseMortgage-Backed Securities - By Type (Details) (USD $)NoRoundingUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.biminicapital.com/role/DisclosureMortgageBackedSecuritiesByTypeDetails226