XML 32 R30.htm IDEA: XBRL DOCUMENT v2.4.1.9
Mortgage Backed Securities Mortgage backed securities designated as AFS (Details) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale MBS, Par Balance $ 2,621,540,000us-gaap_InvestmentOwnedBalancePrincipalAmount $ 3,254,946,000us-gaap_InvestmentOwnedBalancePrincipalAmount  
Available-for-sale MBS, Unamortized Premium (Discount) 868,984,000dx_InvestmentsUnamortizedPremiumDiscount 758,950,000dx_InvestmentsUnamortizedPremiumDiscount  
Available-for-sale MBS, Amortized Cost 3,490,524,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis 4,013,896,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis  
Available-for-sale Debt Securities, Gross Unrealized Gain 48,868,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax 45,114,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax  
Available-for-sale MBS, Gross Unrealized Loss (23,153,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax (69,566,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax  
Available-for-sale MBS, Fair Value 3,516,239,000us-gaap_AvailableForSaleSecuritiesDebtSecurities 3,989,444,000us-gaap_AvailableForSaleSecuritiesDebtSecurities  
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds 503,918,000us-gaap_AvailableForSaleSecuritiesGrossRealizedGainsLossesSaleProceeds 357,892,000us-gaap_AvailableForSaleSecuritiesGrossRealizedGainsLossesSaleProceeds 125,108,000us-gaap_AvailableForSaleSecuritiesGrossRealizedGainsLossesSaleProceeds
Available-for-sale Securities, Gross Realized Gains 22,492,000us-gaap_AvailableForSaleSecuritiesGrossRealizedGains 8,670,000us-gaap_AvailableForSaleSecuritiesGrossRealizedGains 5,319,000us-gaap_AvailableForSaleSecuritiesGrossRealizedGains
Available-for-sale Securities, Gross Realized Losses (6,269,000)us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses (5,316,000)us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses 0us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses
Available-for-sale Securities, Gross Realized Gain (Loss) 16,223,000us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet 3,354,000us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet 5,319,000us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet [1]
Residential Mortgage Backed Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale MBS, Par Balance 2,109,239,000us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember		 2,605,413,000us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember		  
Available-for-sale MBS, Unamortized Premium (Discount) 113,618,000dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember		 153,882,000dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember		  
Available-for-sale MBS, Amortized Cost 2,222,857,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember		 2,759,295,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember		  
Available-for-sale Debt Securities, Gross Unrealized Gain 8,580,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember		 6,442,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember		  
Available-for-sale MBS, Gross Unrealized Loss (22,289,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember		 (59,822,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember		  
Available-for-sale MBS, Fair Value 2,209,148,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember		 2,705,915,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember		  
Commercial Mortgage Backed Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale MBS, Par Balance 512,301,000us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember		 649,533,000us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember		  
Available-for-sale MBS, Unamortized Premium (Discount) 9,522,000dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember		 784,000dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember		  
Available-for-sale MBS, Amortized Cost 521,823,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember		 650,317,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember		  
Available-for-sale Debt Securities, Gross Unrealized Gain 21,967,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember		 26,159,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember		  
Available-for-sale MBS, Gross Unrealized Loss (555,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember		 (4,411,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember		  
Available-for-sale MBS, Fair Value 543,235,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember		 672,065,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember		  
CMBS IO [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale MBS, Par Balance 0us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember		 0us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember		  
Available-for-sale MBS, Unamortized Premium (Discount) 745,844,000dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember		 604,284,000dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember		  
Available-for-sale MBS, Amortized Cost 745,844,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember		 604,284,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember		  
Available-for-sale Debt Securities, Gross Unrealized Gain 18,321,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember		 12,513,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember		  
Available-for-sale MBS, Gross Unrealized Loss (309,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember		 (5,333,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember		  
Available-for-sale MBS, Fair Value 763,856,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember		 611,464,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember		  
Agency MBS [Member] | Residential Mortgage Backed Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale MBS, Par Balance 2,086,807,000us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 2,591,568,000us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale MBS, Unamortized Premium (Discount) 113,635,000dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 154,220,000dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale MBS, Amortized Cost 2,200,442,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 2,745,788,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale Debt Securities, Gross Unrealized Gain 8,473,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 6,104,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale MBS, Gross Unrealized Loss (22,215,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 (59,742,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale MBS, Fair Value 2,186,700,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 2,692,150,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale MBS, Weighted Average Coupon 3.09%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 [2] 3.22%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 [3]  
Agency MBS [Member] | Commercial Mortgage Backed Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale MBS, Par Balance 301,943,000us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 273,830,000us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale MBS, Unamortized Premium (Discount) 18,042,000dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 19,061,000dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale MBS, Amortized Cost 319,985,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 292,891,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 [4]  
Available-for-sale Debt Securities, Gross Unrealized Gain 15,288,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 10,793,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale MBS, Gross Unrealized Loss (76,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 (900,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale MBS, Fair Value 335,197,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 302,784,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 [4]  
Available-for-sale MBS, Weighted Average Coupon 5.21%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 [2] 5.07%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 [3]  
Agency MBS [Member] | CMBS IO [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale MBS, Par Balance 0us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 [5] 0us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 [6]  
Available-for-sale MBS, Unamortized Premium (Discount) 426,564,000dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 453,766,000dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale MBS, Amortized Cost 426,564,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 453,766,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale Debt Securities, Gross Unrealized Gain 12,252,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 9,895,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale MBS, Gross Unrealized Loss (79,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 (3,334,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale MBS, Fair Value 438,737,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 460,327,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale MBS, Weighted Average Coupon 0.80%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 [2] 0.83%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 [3]  
Notional balance for interest only securities 10,460,113,000dx_Notionalbalanceforinterestonlysecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 10,160,502,000dx_Notionalbalanceforinterestonlysecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Non-Agency MBS [Member] | Residential Mortgage Backed Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale MBS, Par Balance 22,432,000us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 13,845,000us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale MBS, Unamortized Premium (Discount) (17,000)dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 (338,000)dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale MBS, Amortized Cost 22,415,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 13,507,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale Debt Securities, Gross Unrealized Gain 107,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 338,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale MBS, Gross Unrealized Loss (74,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 (80,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale MBS, Fair Value 22,448,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 13,765,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale MBS, Weighted Average Coupon 3.83%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 [2] 4.61%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 [3]  
Non-Agency MBS [Member] | Commercial Mortgage Backed Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale MBS, Par Balance 210,358,000us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 375,703,000us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale MBS, Unamortized Premium (Discount) (8,520,000)dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 (18,277,000)dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale MBS, Amortized Cost 201,838,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 357,426,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale Debt Securities, Gross Unrealized Gain 6,679,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 15,366,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale MBS, Gross Unrealized Loss (479,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 (3,511,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale MBS, Fair Value 208,038,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 369,281,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale MBS, Weighted Average Coupon 4.33%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 [2] 5.10%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 [3]  
Non-Agency MBS [Member] | CMBS IO [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale MBS, Par Balance 0us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 [5]    
Available-for-sale MBS, Unamortized Premium (Discount) 319,280,000dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 150,518,000dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale MBS, Amortized Cost 319,280,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 150,518,000us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale Debt Securities, Gross Unrealized Gain 6,069,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 2,618,000us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale MBS, Gross Unrealized Loss (230,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 (1,999,000)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale MBS, Fair Value 325,119,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 151,137,000us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale MBS, Weighted Average Coupon 0.72%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 [2] 0.66%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 [3]  
Notional balance for interest only securities 7,868,896,000dx_Notionalbalanceforinterestonlysecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 4,274,957,000dx_Notionalbalanceforinterestonlysecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Agency MBS [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale MBS, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value 322,741,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 1,912,937,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 879,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 43,543,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale MBS, Number of Securities in Continuous Unrealized Loss Position for Less than One Year 24us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 150us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale MBS, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value 1,321,323,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 670,402,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss 21,491,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 20,433,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Available-for-sale MBS, Number of Securities in Continuous Unrealized Loss Position for Greater than or Equal to One Year 113us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 67us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		  
Non-Agency MBS [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale MBS, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value 111,778,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 162,558,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 625,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 5,435,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale MBS, Number of Securities in Continuous Unrealized Loss Position for Less than One Year 24us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 39us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale MBS, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value 18,037,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 6,310,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss $ 159,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 $ 155,000us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
Available-for-sale MBS, Number of Securities in Continuous Unrealized Loss Position for Greater than or Equal to One Year 5us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		 6us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember		  
[1] (1) Total gain on sale of investments, net for the year ended December 31, 2012 includes $2,072 and $1,070 of gains recognized from the Company's liquidation of a securitized mortgage loan and an investment in Freddie Mac Unsecured Senior Notes, respectively, which are not included in this table.
[2] (1) The current weighted average coupon ("WAC") is the gross interest rate of the pool of mortgages underlying the security weighted by the outstanding principal balance (or by notional balance in the case of an IO security).
[3] (1)The current weighted average coupon ("WAC") is the gross interest rate of the pool of mortgages underlying the security weighted by the outstanding principal balance (or by notional balance in the case of an IO security).
[4] (2) As of December 31, 2013, the Company had Agency CMBS with an amortized cost of $26,920 and fair value of $28,717 which were designated as trading securities and are not included in this table. The Company changed the designation of these Agency CMBS to AFS during the three months ended June 30, 2014. Changes in the fair value of these MBS while they were designated as trading were recognized in net income within "fair value adjustments, net". Changes in the fair value of these MBS, which are now designated as AFS, are recognized in "other comprehensive income". As of December 31, 2014, the Company does not have any MBS designated as trading.
[5] (2)The notional balance for Agency CMBS IO and non-Agency CMBS IO was $10,460,113 and $7,868,896, respectively, as of December 31, 2014.
[6] (3) The notional balance for the Agency CMBS IO and non-Agency CMBS IO was $10,160,502 and $4,274,957, respectively, as of December 31, 2013.