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Mortgage Loans Held for Investment, at Fair Value (Parenthetical Information) (Details) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Distressed and Re-performing Loans [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Change in unrealized gain or loss on investments $ 22,800,000us-gaap_FairValueOptionChangesInFairValueGainLoss1
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= zfc_DistressedAndReperformingLoansMember		 $ 7,100,000us-gaap_FairValueOptionChangesInFairValueGainLoss1
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= zfc_DistressedAndReperformingLoansMember
Threshold period past due after which loans are considered considered non-performing 60 days  
Newly Originated Mortgage Loans [Member]    
Fair Value, Option, Quantitative Disclosures [Line Items]    
Change in unrealized gain or loss on investments $ 3,538us-gaap_FairValueOptionChangesInFairValueGainLoss1
/ us-gaap_EligibleItemOrGroupForFairValueOptionAxis
= zfc_NewlyOriginatedMortgageLoansMember