XML 26 R22.htm IDEA: XBRL DOCUMENT v2.4.1.9
Mortgage Backed Securities Mortgage backed securities designated as AFS (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale MBS, Par Balance $ 2,976,821us-gaap_InvestmentOwnedBalancePrincipalAmount   $ 2,621,540us-gaap_InvestmentOwnedBalancePrincipalAmount
Available-for-sale MBS, Unamortized Premium (Discount) 855,191dx_InvestmentsUnamortizedPremiumDiscount   868,984dx_InvestmentsUnamortizedPremiumDiscount
Available-for-sale MBS, Amortized Cost 3,832,012us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis   3,490,524us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Available-for-sale Debt Securities, Gross Unrealized Gain 61,411us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax   48,868us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Available-for-sale MBS, Gross Unrealized Loss (13,700)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax   (23,153)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Available-for-sale MBS, Fair Value 3,879,723us-gaap_AvailableForSaleSecuritiesDebtSecurities   3,516,239us-gaap_AvailableForSaleSecuritiesDebtSecurities
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds 102,923us-gaap_AvailableForSaleSecuritiesGrossRealizedGainsLossesSaleProceeds 59,799us-gaap_AvailableForSaleSecuritiesGrossRealizedGainsLossesSaleProceeds  
Available-for-sale Securities, Gross Realized Gains 1,773us-gaap_AvailableForSaleSecuritiesGrossRealizedGains 219us-gaap_AvailableForSaleSecuritiesGrossRealizedGains  
Available-for-sale Securities, Gross Realized Losses (465)us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses (3,526)us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses  
Available-for-sale Securities, Gross Realized Gain (Loss) 1,308us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet (3,307)us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet  
Residential Mortgage Backed Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale MBS, Par Balance 2,018,979us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
  2,109,239us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
Available-for-sale MBS, Unamortized Premium (Discount) 104,283dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
  113,618dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
Available-for-sale MBS, Amortized Cost 2,123,262us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
  2,222,857us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
Available-for-sale Debt Securities, Gross Unrealized Gain 11,414us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
  8,580us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
Available-for-sale MBS, Gross Unrealized Loss (13,154)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
  (22,289)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
Available-for-sale MBS, Fair Value 2,121,522us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
  2,209,148us-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 957,842us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
  512,301us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
Available-for-sale MBS, Unamortized Premium (Discount) 8,870dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
  9,522dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
Available-for-sale MBS, Amortized Cost 966,712us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
  521,823us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
Available-for-sale Debt Securities, Gross Unrealized Gain 27,834us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
  21,967us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
Available-for-sale MBS, Gross Unrealized Loss (534)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
  (555)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
Available-for-sale MBS, Fair Value 994,012us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
  543,235us-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) 742,038dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
  745,844dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
Available-for-sale MBS, Amortized Cost 742,038us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
  745,844us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
Available-for-sale Debt Securities, Gross Unrealized Gain 22,163us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
  18,321us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
Available-for-sale MBS, Gross Unrealized Loss (12)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
  (309)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
Available-for-sale MBS, Fair Value 764,189us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
  763,856us-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 1,942,332us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  2,086,807us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale MBS, Unamortized Premium (Discount) 104,352dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  113,635dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale MBS, Amortized Cost 2,046,684us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  2,200,442us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale Debt Securities, Gross Unrealized Gain 11,271us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  8,473us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale MBS, Gross Unrealized Loss (13,075)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  (22,215)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale MBS, Fair Value 2,044,880us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  2,186,700us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale MBS, Weighted Average Coupon 3.08%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
[1]   3.09%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
[2]
Agency MBS [Member] | Commercial Mortgage Backed Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale MBS, Par Balance 740,363us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  301,943us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale MBS, Unamortized Premium (Discount) 17,321dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  18,042dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale MBS, Amortized Cost 757,684us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  319,985us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale Debt Securities, Gross Unrealized Gain 20,234us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  15,288us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale MBS, Gross Unrealized Loss (171)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  (76)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale MBS, Fair Value 777,747us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  335,197us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale MBS, Weighted Average Coupon 3.68%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
[1]   5.21%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
[2]
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
[3]   0us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
[4]
Available-for-sale MBS, Unamortized Premium (Discount) 410,948dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  426,564dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale MBS, Amortized Cost     426,564us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale Debt Securities, Gross Unrealized Gain 13,257us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  12,252us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale MBS, Gross Unrealized Loss (12)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  (79)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale MBS, Fair Value 424,193us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  438,737us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale MBS, Weighted Average Coupon 0.87%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
[1]   0.80%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
[2]
Notional balance for interest only securities 10,415,002dx_Notionalbalanceforinterestonlysecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  10,460,113dx_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 76,647us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  22,432us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Available-for-sale MBS, Unamortized Premium (Discount) (69)dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  (17)dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Available-for-sale MBS, Amortized Cost 76,578us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  22,415us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Available-for-sale Debt Securities, Gross Unrealized Gain 143us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  107us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Available-for-sale MBS, Gross Unrealized Loss (79)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  (74)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Available-for-sale MBS, Fair Value 76,642us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  22,448us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Available-for-sale MBS, Weighted Average Coupon 3.57%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
[1]   3.83%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_ResidentialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
[2]
Non-Agency MBS [Member] | Commercial Mortgage Backed Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Available-for-sale MBS, Par Balance 217,479us-gaap_InvestmentOwnedBalancePrincipalAmount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
   
Available-for-sale MBS, Unamortized Premium (Discount) (8,451)dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
   
Available-for-sale MBS, Amortized Cost 209,028us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
   
Available-for-sale Debt Securities, Gross Unrealized Gain 7,600us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
   
Available-for-sale MBS, Gross Unrealized Loss (363)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
   
Available-for-sale MBS, Fair Value 216,265us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  208,038us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Available-for-sale MBS, Weighted Average Coupon 4.23%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
[1]   5.10%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
[2]
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
[3]    
Available-for-sale MBS, Unamortized Premium (Discount) 331,090dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  319,280dx_InvestmentsUnamortizedPremiumDiscount
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Available-for-sale MBS, Amortized Cost 331,090us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  319,280us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Available-for-sale Debt Securities, Gross Unrealized Gain 8,906us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  6,069us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Available-for-sale MBS, Gross Unrealized Loss 0us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  (230)us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Available-for-sale MBS, Fair Value 339,996us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  325,119us-gaap_AvailableForSaleSecuritiesDebtSecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Available-for-sale MBS, Weighted Average Coupon 0.71%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
[1]   0.72%dx_InvestmentsWeightedAverageCouponRate
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
[2]
Notional balance for interest only securities 9,115,887dx_Notionalbalanceforinterestonlysecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_InterestOnlyStripMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  7,868,896dx_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 261,035us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  322,741us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 531us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  879us-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 17us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  24us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale MBS, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value 1,030,027us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  1,321,323us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss 12,727us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  21,491us-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 91us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
  113us-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 79,310us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  111,778us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 382us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  625us-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 13us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  24us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Available-for-sale MBS, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value 1,224us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  18,037us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss $ 61us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  $ 159us-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 4us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
  5us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsGreaterThanOrEqualToOneYear
/ us-gaap_FairValueByAssetClassAxis
= us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
[1] (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).
[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] (2)The notional balance for Agency CMBS IO and non-Agency CMBS IO was $10,415,002 and $9,115,887, respectively, as of March 31, 2015.
[4] (2) The notional balance for the Agency CMBS IO and non-Agency CMBS IO was $10,460,113 and $7,868,896, respectively, as of December 31, 2014.