| REAL ESTATE SECURITIES - Geographic Distribution of Collateral Securing Newcastle's CMBS and ABS (Details 4) (USD $) In Thousands, unless otherwise specified | Mar. 31, 2015 | 
|---|---|
| CMBS [Member] | |
| Principal balance | $ 209,371us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 
| Percentage of principal balance | 100.00%us-gaap_InvestmentOwnedPercentOfNetAssets / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 
| CMBS [Member] | Western US [Member] | |
| Principal balance | 28,315us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_ConcentrationRiskByTypeAxis = nct_WesternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 
| Percentage of principal balance | 13.50%us-gaap_InvestmentOwnedPercentOfNetAssets / us-gaap_ConcentrationRiskByTypeAxis = nct_WesternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 
| CMBS [Member] | Northeastern US [Member] | |
| Principal balance | 58,336us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_ConcentrationRiskByTypeAxis = nct_NortheasternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 
| Percentage of principal balance | 27.80%us-gaap_InvestmentOwnedPercentOfNetAssets / us-gaap_ConcentrationRiskByTypeAxis = nct_NortheasternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 
| CMBS [Member] | Southeastern US [Member] | |
| Principal balance | 44,957us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_ConcentrationRiskByTypeAxis = nct_SoutheasternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 
| Percentage of principal balance | 21.50%us-gaap_InvestmentOwnedPercentOfNetAssets / us-gaap_ConcentrationRiskByTypeAxis = nct_SoutheasternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 
| CMBS [Member] | Midwestern US [Member] | |
| Principal balance | 35,954us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_ConcentrationRiskByTypeAxis = nct_MidwesternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 
| Percentage of principal balance | 17.20%us-gaap_InvestmentOwnedPercentOfNetAssets / us-gaap_ConcentrationRiskByTypeAxis = nct_MidwesternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 
| CMBS [Member] | Southwestern US [Member] | |
| Principal balance | 27,605us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_ConcentrationRiskByTypeAxis = nct_SouthwesternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 
| Percentage of principal balance | 13.20%us-gaap_InvestmentOwnedPercentOfNetAssets / us-gaap_ConcentrationRiskByTypeAxis = nct_SouthwesternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 
| CMBS [Member] | Other Locations [Member] | |
| Principal balance | 10,825us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_ConcentrationRiskByTypeAxis = nct_OtherLocationsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 
| Percentage of principal balance | 5.20%us-gaap_InvestmentOwnedPercentOfNetAssets / us-gaap_ConcentrationRiskByTypeAxis = nct_OtherLocationsMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 
| CMBS [Member] | Foreign [Member] | |
| Principal balance | 3,379us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_ConcentrationRiskByTypeAxis = nct_ForeignMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 
| Percentage of principal balance | 1.60%us-gaap_InvestmentOwnedPercentOfNetAssets / us-gaap_ConcentrationRiskByTypeAxis = nct_ForeignMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CommercialMortgageBackedSecuritiesMember | 
| ABS [Member] | |
| Principal balance | 73,184us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 
| Percentage of principal balance | 100.00%us-gaap_InvestmentOwnedPercentOfNetAssets / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 
| ABS [Member] | Western US [Member] | |
| Principal balance | 20,229us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_ConcentrationRiskByTypeAxis = nct_WesternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 
| Percentage of principal balance | 27.60%us-gaap_InvestmentOwnedPercentOfNetAssets / us-gaap_ConcentrationRiskByTypeAxis = nct_WesternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 
| ABS [Member] | Northeastern US [Member] | |
| Principal balance | 18,903us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_ConcentrationRiskByTypeAxis = nct_NortheasternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 
| Percentage of principal balance | 25.80%us-gaap_InvestmentOwnedPercentOfNetAssets / us-gaap_ConcentrationRiskByTypeAxis = nct_NortheasternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 
| ABS [Member] | Southeastern US [Member] | |
| Principal balance | 16,215us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_ConcentrationRiskByTypeAxis = nct_SoutheasternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 
| Percentage of principal balance | 22.20%us-gaap_InvestmentOwnedPercentOfNetAssets / us-gaap_ConcentrationRiskByTypeAxis = nct_SoutheasternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 
| ABS [Member] | Midwestern US [Member] | |
| Principal balance | 9,743us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_ConcentrationRiskByTypeAxis = nct_MidwesternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 
| Percentage of principal balance | 13.30%us-gaap_InvestmentOwnedPercentOfNetAssets / us-gaap_ConcentrationRiskByTypeAxis = nct_MidwesternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 
| ABS [Member] | Southwestern US [Member] | |
| Principal balance | $ 8,094us-gaap_InvestmentOwnedBalancePrincipalAmount / us-gaap_ConcentrationRiskByTypeAxis = nct_SouthwesternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 
| Percentage of principal balance | 11.10%us-gaap_InvestmentOwnedPercentOfNetAssets / us-gaap_ConcentrationRiskByTypeAxis = nct_SouthwesternUSMember / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_AssetBackedSecuritiesMember | 
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- Definition For investments which are quantified by principal amount, the principle balance held at close of period. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Percent of net assets at close of period. For schedules of investments that are categorized, each category has a percent of net assets for the aggregated value of the Investments in the category. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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