XML 47 R26.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Derivatives (Details) (USD $) In Thousands, unless otherwise specified | 3 Months Ended |
--- | --- | ---
Mar. 31, 2015 | Mar. 31, 2014 | Dec. 31, 2014
Derivative [Line Items] |  |  |  |  |
Derivative assets, fair value | $ 8,079us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue |  |  | $ 5,727us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue |
Derivative liabilities, fair value | (57,168)us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue |  |  | (35,898)us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue |
Notional amount of derivative instruments added | 815,000dx_NotionalAmountofDerivativeInstrumentsAdded |  |  |  |
Notional amount of derivative instruments terminated | (205,000)dx_NotionalAmountofDerivativeInstrumentsTerminated |  |  |  |
Derivatives, notional amount | 18,135,000invest_DerivativeNotionalAmount |  |  | 17,525,000invest_DerivativeNotionalAmount |
Gain (loss) on derivative instruments, net | (25,323)us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet |  | (13,422)us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet |  |
Not Designated as Hedging Instrument [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative assets, aggregate notional amount | 510,000us-gaap_DerivativeAssetNotionalAmount / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember |  |  | 440,000us-gaap_DerivativeAssetNotionalAmount / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember |
Derivative liabilities, aggregate notional amount | 17,625,000us-gaap_DerivativeLiabilityNotionalAmount / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember |  |  | 17,085,000us-gaap_DerivativeLiabilityNotionalAmount / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember |
Forward Contracts [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivatives, notional amount | 425,000invest_DerivativeNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForwardContractsMember |  |  |  |
Weighted-average Fixed Pay Rate | 1.98%us-gaap_DerivativeAverageFixedInterestRate / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForwardContractsMember |  |  |  |
Weighted-average Fixed Receive Rate | 1.98%us-gaap_DerivativeAverageFixedInterestRate / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_ForwardContractsMember |  |  |  |
Interest Rate Swap [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative assets, fair value | 8,079us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember |  |  | 5,727us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember |
Derivative liabilities, fair value | (7,784)us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember |  |  | (3,002)us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember |
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative assets, aggregate notional amount | 510,000us-gaap_DerivativeAssetNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember |  |  | 440,000us-gaap_DerivativeAssetNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember |
Derivative liabilities, aggregate notional amount | 1,025,000us-gaap_DerivativeLiabilityNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember |  |  | 485,000us-gaap_DerivativeLiabilityNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember |
Eurodollar Future [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative assets, fair value | 0us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EurodollarFutureMember |  |  |  |
Derivative liabilities, fair value | (49,384)us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EurodollarFutureMember |  |  | (32,896)us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EurodollarFutureMember |
Notional amount of derivative instruments added | 0dx_NotionalAmountofDerivativeInstrumentsAdded / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EurodollarFutureMember |  |  |  |
Notional amount of derivative instruments terminated | 0dx_NotionalAmountofDerivativeInstrumentsTerminated / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EurodollarFutureMember |  |  |  |
Derivatives, notional amount | 16,600,000invest_DerivativeNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EurodollarFutureMember |  |  | 16,600,000invest_DerivativeNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EurodollarFutureMember |
Gain (loss) on derivative instruments, net | (16,488)us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EurodollarFutureMember |  | (4,414)us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EurodollarFutureMember |  |
Eurodollar Future [Member] | Not Designated as Hedging Instrument [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative assets, aggregate notional amount | 0us-gaap_DerivativeAssetNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EurodollarFutureMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember | [1] |  |  |
Derivative liabilities, aggregate notional amount | 16,600,000us-gaap_DerivativeLiabilityNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EurodollarFutureMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember | [1] |  | 16,600,000us-gaap_DerivativeLiabilityNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_EurodollarFutureMember / us-gaap_HedgingDesignationAxis = us-gaap_NondesignatedMember | [1]
Long [Member] | Interest Rate Swap [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Notional amount of derivative instruments added | 0dx_NotionalAmountofDerivativeInstrumentsAdded / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Notional amount of derivative instruments terminated | 0dx_NotionalAmountofDerivativeInstrumentsTerminated / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Derivatives, notional amount | 275,000invest_DerivativeNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  | 275,000invest_DerivativeNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |
Gain (loss) on derivative instruments, net | 4,528us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  | 0us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |
Long [Member] | Interest Rate Swap [Member] | Interest Rate Swap Agreements, Maturities in Next 37-48 Months [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivatives, notional amount | 0invest_DerivativeNotionalAmount / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext3748MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Weighted-average Fixed Pay Rate | 0.00%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext3748MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Weighted-average Fixed Receive Rate | 0.00%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext3748MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Long [Member] | Interest Rate Swap [Member] | Interest Rate Swap Agreements, Maturities in Next 49-60 Months [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivatives, notional amount | 250,000invest_DerivativeNotionalAmount / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext4960MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Weighted-average Fixed Pay Rate | 1.91%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext4960MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Weighted-average Fixed Receive Rate | 1.91%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext4960MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Long [Member] | Interest Rate Swap [Member] | Interest Rate Swap Agreements, Maturities in Next 61-72 Months [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivatives, notional amount | 0invest_DerivativeNotionalAmount / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext6172MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Weighted-average Fixed Pay Rate | 0.00%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext6172MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Weighted-average Fixed Receive Rate | 0.00%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext6172MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Long [Member] | Interest Rate Swap [Member] | Interest Rate Swap Agreements, Maturities in Next 73-84 Months [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivatives, notional amount | 0invest_DerivativeNotionalAmount / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext7384MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Weighted-average Fixed Pay Rate | 0.00%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext7384MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Weighted-average Fixed Receive Rate | 0.00%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext7384MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Long [Member] | Interest Rate Swap [Member] | Interest Rate Swap Agreements, Maturities in Next 85-96 Months [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivatives, notional amount | 0invest_DerivativeNotionalAmount / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext8596MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Weighted-average Fixed Pay Rate | 0.00%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext8596MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Weighted-average Fixed Receive Rate | 0.00%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext8596MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Long [Member] | Interest Rate Swap [Member] | Interest Rate Swap Agreements, Maturities in Next 97-108 Months [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivatives, notional amount | 0invest_DerivativeNotionalAmount / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext97108MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Weighted-average Fixed Pay Rate | 0.00%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext97108MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Weighted-average Fixed Receive Rate | 0.00%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext97108MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Long [Member] | Interest Rate Swap [Member] | Interest Rate Swap Agreements, Maturities in Next 109-120 Months [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivatives, notional amount | 25,000invest_DerivativeNotionalAmount / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext109120MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Weighted-average Fixed Pay Rate | 2.71%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext109120MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Weighted-average Fixed Receive Rate | 2.71%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext109120MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_LongMember |  |  |  |
Short [Member] | Interest Rate Swap [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Notional amount of derivative instruments added | 815,000dx_NotionalAmountofDerivativeInstrumentsAdded / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Notional amount of derivative instruments terminated | (205,000)dx_NotionalAmountofDerivativeInstrumentsTerminated / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Derivatives, notional amount | 1,260,000invest_DerivativeNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  | 650,000invest_DerivativeNotionalAmount / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |
Gain (loss) on derivative instruments, net | (13,363)us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  | (9,008)us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |
Short [Member] | Interest Rate Swap [Member] | Interest Rate Swap Agreements, Maturities in Next 37-48 Months [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivatives, notional amount | 385,000invest_DerivativeNotionalAmount / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext3748MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Weighted-average Fixed Pay Rate | 1.21%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext3748MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Weighted-average Fixed Receive Rate | 1.21%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext3748MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Short [Member] | Interest Rate Swap [Member] | Interest Rate Swap Agreements, Maturities in Next 49-60 Months [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivatives, notional amount | 470,000invest_DerivativeNotionalAmount / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext4960MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Weighted-average Fixed Pay Rate | 1.74%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext4960MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Weighted-average Fixed Receive Rate | 1.74%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext4960MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Short [Member] | Interest Rate Swap [Member] | Interest Rate Swap Agreements, Maturities in Next 61-72 Months [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivatives, notional amount | 25,000invest_DerivativeNotionalAmount / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext6172MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Weighted-average Fixed Pay Rate | 1.61%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext6172MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Weighted-average Fixed Receive Rate | 1.61%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext6172MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Short [Member] | Interest Rate Swap [Member] | Interest Rate Swap Agreements, Maturities in Next 73-84 Months [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivatives, notional amount | 75,000invest_DerivativeNotionalAmount / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext7384MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Weighted-average Fixed Pay Rate | 1.77%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext7384MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Weighted-average Fixed Receive Rate | 1.77%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext7384MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Short [Member] | Interest Rate Swap [Member] | Interest Rate Swap Agreements, Maturities in Next 85-96 Months [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivatives, notional amount | 125,000invest_DerivativeNotionalAmount / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext8596MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Weighted-average Fixed Pay Rate | 1.98%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext8596MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Weighted-average Fixed Receive Rate | 1.98%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext8596MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Short [Member] | Interest Rate Swap [Member] | Interest Rate Swap Agreements, Maturities in Next 97-108 Months [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivatives, notional amount | 0invest_DerivativeNotionalAmount / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext97108MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Weighted-average Fixed Pay Rate | 0.00%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext97108MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Weighted-average Fixed Receive Rate | 0.00%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext97108MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Short [Member] | Interest Rate Swap [Member] | Interest Rate Swap Agreements, Maturities in Next 109-120 Months [Member] |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivatives, notional amount | $ 180,000invest_DerivativeNotionalAmount / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext109120MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Weighted-average Fixed Pay Rate | 2.07%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext109120MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
Weighted-average Fixed Receive Rate | 2.07%us-gaap_DerivativeAverageFixedInterestRate / dx_DerivativeInstrumentMaturityScheduleAxis = dx_InterestRateSwapAgreementsMaturitiesinNext109120MonthsMember / us-gaap_DerivativeInstrumentRiskAxis = us-gaap_InterestRateSwapMember / us-gaap_PositionAxis = us-gaap_ShortMember |  |  |  |
[1] | The Eurodollar futures aggregate notional amount represents the total notional of the 3-month contracts with expiration dates from 2015 to 2020. The maximum notional outstanding for any future 3-month period did not exceed $1,300,000 as of March 31, 2015 or as of December 31, 2014.

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- Definition Aggregate notional amount terminated in the period specified by the derivative(s). Expressed as an absolute value. + References No definition available. + Details
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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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