Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2013
Accounting Policies [Abstract]
Nature of Operations [Text Block]	Organization Dynex Capital, Inc., ("Company”) was incorporated in the Commonwealth of Virginia on December 18, 1987 and commenced operations in February 1988. The Company primarily earns income from investing on a leveraged basis in mortgage-backed securities ("MBS") that are issued or guaranteed by the U.S. Government or U.S. Government sponsored agencies ("Agency MBS") and MBS issued by others ("non-Agency MBS").
Basis of Presentation [Policy Text Block]	Basis of Presentation The accompanying consolidated financial statements of Dynex Capital, Inc. and its qualified real estate investment trust ("REIT") subsidiaries and its taxable REIT subsidiary (together, "Dynex" or the "Company") have been prepared in accordance with the generally accepted accounting principles in the United States ("GAAP") and the instructions to the Annual Report on Form 10-K and Article 3 of Regulation S-X promulgated by the Securities and Exchange Commission (the "SEC").
Reclassification, Policy [Policy Text Block]	Reclassifications Certain items in the prior years' consolidated financial statements have been reclassified to conform to the current year’s presentation. The Company’s consolidated balance sheet as of December 31, 2012 now presents its Agency and non-Agency mortgage-backed securities as "mortgage-backed securities, at fair value". The Company's consolidated statements of net income for the years ended December 31, 2012 and December 31, 2011 now present interest income from Agency and non-Agency mortgage-backed securities together as "interest income: mortgage-backed securities". In addition, changes in fair value and other activity related to the Company's derivative instruments have been reclassified from "fair value adjustments, net" to "loss on derivative instruments, net". As a result, the respective amounts on the Company's consolidated statements of cash flow for the years ended December 31, 2012 and December 31, 2011 have been changed to reflect this reclassification. These presentation changes have no effect on reported total assets, total liabilities, results of operations, or cash flow activities.
Consolidation [Policy Text Block]	Consolidation The consolidated financial statements include the accounts of the Company, its qualified REIT subsidiaries and its taxable REIT subsidiary. The consolidated financial statements represent the Company’s accounts after the elimination of intercompany balances and transactions. The Company consolidates entities in which it owns more than 50% of the voting equity and control does not rest with others and variable interest entities in which it is determined to be the primary beneficiary in accordance with Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("ASC") Topic 810-10. The Company follows the equity method of accounting for investments in which it owns greater than a 20% and less than 50% interest in partnerships and corporate joint ventures or when it is able to influence the financial and operating policies of the investee but owns less than 50% of the voting equity. The Company did not have any investments in which it owned less than a 50% interest in the voting equity as of December 31, 2013 or December 31, 2012. In accordance with ASC Topic 810-10, the Company also consolidates certain trusts through which it has securitized mortgage loans. Additional information regarding the accounting policy for securitized mortgage loans is provided below under "Investments".
Use of Estimates [Policy Text Block]	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements as well as the reported amounts of revenue and expenses during the reported period. Actual results could differ from those estimates. The most significant estimates used by management include but are not limited to fair value measurements of its investments, allowance for loan losses, other-than-temporary impairments, contingencies, and amortization of premiums and discounts. These items are discussed further below within this note to the consolidated financial statements.
Federal Income Taxes [Policy Text Block]	Federal Income Taxes The Company believes it has complied with the requirements for qualification as a REIT under the Internal Revenue Code of 1986, as amended (the "Code"). As such, the Company believes that it qualifies as a REIT for federal income tax purposes, and it generally will not be subject to federal income tax on the amount of its income or gain that is distributed as dividends to shareholders. The Company uses the calendar year for both tax and financial reporting purposes. There may be differences between taxable income and income computed in accordance with GAAP.
Cash and Cash Equivalents [Policy Text Block]	Cash and Cash Equivalents Cash and cash equivalents include cash on hand and highly liquid investments with original maturities of three months or less.
Restricted Cash [Policy Text Block]	Restricted Cash Restricted cash consists of cash the Company has pledged to cover initial and variation margin with its counterparties.
Investments [Policy Text Block]	Mortgage-Backed Securities In accordance with ASC Topic 320, the Company has designated the majority of its investments in MBS as available-for-sale ("AFS"), and the remainder is designated as trading. All of the Company’s MBS are recorded at their fair value on its consolidated balance sheet. Changes in fair value for the Company's AFS securities are reported in other comprehensive income ("OCI") until the security is collected, disposed of, or determined to be other than temporarily impaired. Although the Company generally intends to hold its AFS securities until maturity, it may, from time to time, sell any of these securities as part of the overall management of its business. Upon the sale of an AFS security, any unrealized gain or loss is reclassified out of accumulated other comprehensive income ("AOCI") into net income as a realized "gain (loss) on sale of investments, net" using the specific identification method. Changes in the fair value of MBS designated as trading are recognized in net income within "fair value adjustments, net". Gains and losses realized upon the sale, impairment, or other disposal of a trading security are also recognized within "fair value adjustments, net". The Company’s MBS pledged as collateral against repurchase agreements and derivative instruments are included in MBS on the consolidated balance sheets with the fair value of the MBS pledged disclosed parenthetically. Interest Income, Premium Amortization, and Discount Accretion. Interest income on MBS is accrued based on the outstanding principal balance (or notional balance in the case of interest-only, or "IO", securities) and their contractual terms. Premiums and discounts on Agency MBS as well as any non-Agency MBS rated AA and higher at the time of purchase are amortized into interest income over the expected life of such securities using the effective yield method and adjustments to premium amortization are made for actual prepayment activity as well as changes in projected future cash flows in accordance with ASC Topic 310-20. The Company's projections of future cash flows are based on input and analysis received from external sources and internal models, and includes assumptions about the amount and timing of credit losses, loan prepayment rates, fluctuations in interest rates, and other factors. On at least a quarterly basis, the Company reviews and makes any necessary adjustments to its cash flow projections and updates the yield recognized on these assets. The Company has purchased non-Agency MBS rated less than 'AA' by at least one national rating agency at discounts to their par value, and management does not believe these discounts to be substantial. The Company records the discount accretion into income over the security's expected life, which reflects management's estimate of the security's projected cash flows in accordance with ASC Topic 325-40. Future changes in projected cash flows or differences arising between projected cash flows and actual cash flows received may result in a prospective change in the effective yield on those securities. The accrual of interest on MBS is discontinued when, in the opinion of management, it is probable that all amounts contractually due will not be collected, and in certain instances, as a result of an other-than-temporary impairment analysis ("OTTI", see discussion below). All interest accrued but not collected for investments that are placed on a non-accrual status or are charged-off is reversed against interest income. Interest on these investments is accounted for on the cash-basis or cost-recovery method until the affected investment or investments qualify for return to accrual status. Investments are returned to accrual status when all the principal and interest amounts contractually due are brought current and future payments are reasonably assured. Determination of MBS Fair Value. In accordance with ASC Topic 820, the Company determines the fair value for the majority of its MBS based upon prices obtained from third-party pricing services and broker quotes. The remainder of the Company's MBS are valued by discounting the estimated future cash flows derived from cash flow models that utilize information such as the security's coupon rate, estimated prepayment speeds, expected weighted average life, collateral composition, estimated future interest rates, expected losses, and credit enhancements as well as certain other relevant information. The Company's application of ASC Topic 820 guidance is discussed further in Note 9. Other-than-Temporary Impairment. The Company evaluates all MBS in its investment portfolio for other-than-temporary impairments ("OTTI") by comparing the amortized cost of each security in an unrealized loss position against the present value of expected future cash flows of the security. If there has been a significant adverse change in the cash flow expectations for a security resulting in its amortized cost becoming greater than the present value of its expected future cash flows, an other-than-temporary credit impairment has occurred. If the Company does not intend to sell and is not more likely than not required to sell the security, the credit loss is recognized in earnings and the balance of the unrealized loss is recognized in other comprehensive income (loss). If the Company intends to sell the security or will be more likely than not required to sell the security, the full unrealized loss is recognized in earnings. In periods after the recognition of an OTTI for MBS, the Company accounts for the other-than-temporarily impaired MBS as if the MBS had been purchased on the measurement date of the other-than-temporary impairment at an amortized cost basis equal to the previous amortized cost basis less the OTTI recognized in earnings. For MBS for which OTTIs were recognized in earnings, the difference between the new amortized cost basis and the cash flows expected to be collected shall be accreted into interest income using the effective interest method. The Company continues to estimate the present value of cash flows expected to be collected over the life of the MBS. If upon subsequent evaluation, there is an increase in the cash flows expected to be collected or if actual cash flows are greater than cash flows previously expected, such changes shall be accounted for as a prospective adjustment to the accretable yield in accordance with ASC Topic 310-30. Please see Note 3 for additional information related to the Company's evaluation for OTTI.
Securitized Mortgage Loans, Other Investments [Policy Text Block]	Securitized Mortgage Loans Securitized mortgage loans consist of loans pledged to support the repayment of securitization financing bonds issued by the Company. The associated securitization financing bonds are treated as debt of the Company and are presented as a portion of "non-recourse collateralized financing" on the consolidated balance sheet. In accordance with ASC Topic 310-10, the Company's securitized mortgage loans are reported at amortized cost. Securitized mortgage loans can only be sold subject to the lien of the respective securitization financing indenture. An allowance has been established for currently existing and probable losses on such loans in accordance with ASC Topic 310-10. Other Investments Other investments primarily consist of unsecuritized mortgage loans owned by the Company which are accounted for using the cost method in accordance with ASC Topic 325-20. Management evaluates the need for an allowance for loan losses on these unsecuritized mortgage loans in accordance with ASC Topic 310-10 on at least a quarterly basis.
Repurchase Agreements [Policy Text Block]	Repurchase Agreements Repurchase agreements are treated as financings in accordance with the provision of ASC Topic 860 under which the Company pledges its securities as collateral to secure a loan, which is equal in value to a specified percentage of the estimated fair value of the pledged collateral. The Company retains beneficial ownership of the pledged collateral. At the maturity of a repurchase agreement, the Company is required to repay the loan and concurrently receives back its pledged collateral from the lender or, with the consent of the lender, the Company may renew the agreement at the then prevailing financing rate. A repurchase agreement lender may require the Company to pledge additional collateral in the event of a decline in the fair value of the collateral pledged. Repurchase agreement financing is recourse to the Company and the assets pledged. Most of the Company’s repurchase agreements are based on the September 1996 version of the Bond Market Association Master Repurchase Agreement, which generally provides that the lender, as buyer, is responsible for obtaining collateral valuations from a generally recognized source agreed to by both the Company and the lender, or, in an instance when such source is not available, the value determination is made by the lender.
Derivative Instruments [Policy Text Block]	Derivative Instruments The Company accounts for its derivative instruments in accordance with ASC Topic 815. ASC Topic 815 requires an entity to recognize all derivatives as either assets or liabilities in the balance sheet and to measure those instruments at fair value. Effective June 30, 2013, the Company discontinued cash flow hedge accounting for derivative instruments which had previously been accounted for as cash flow hedges under ASC Topic 815. Activity up to and including June 30, 2013 for those agreements previously designated as cash flow hedges was recorded in accordance with cash flow hedge accounting as prescribed by ASC Topic 815, which states that the effective portion of the hedge relationship on an instrument designated as a cash flow hedge is reported in the current period's other comprehensive income while the ineffective portion is immediately reported in the current period’s consolidated statement of net income. The balance remaining in AOCI related to the de-designated cash flow hedges is being recognized in the Company's consolidated statement of net income as a portion of "interest expense" over the remaining life of the interest rate swap agreements. Subsequent to June 30, 2013, changes in the fair value of the Company's derivative instruments, plus periodic settlements, are recorded in the Company's consolidated statement of net income as a portion of "loss on derivative instruments, net". The Company has Eurodollar futures, which are valued based on closing exchange prices. Variation margin is exchanged daily to settle any changes in the value of the Eurodollar futures. Gains and losses associated with purchases and short sales of futures contracts are reported in "(loss) gain on derivative instruments, net" in our consolidated statements of net income. The Company has elected to use the portfolio exception in ASC 820-10-35-18D with respect to measuring counterparty credit risk for derivative instruments. The Company manages credit risk for its derivative positions on a counterparty-by-counterparty basis (that is, on the basis of its net portfolio exposure with each counterparty), consistent with its risk management strategy for such transactions. The Company manages credit risk by considering indicators of risk such as credit ratings, and by negotiating terms in its ISDA master netting arrangements and, if applicable, any associated Credit Support Annex documentation, with each individual counterparty. Since the effective date of ASC 820, management has monitored and measured credit risk and calculated credit valuation adjustments for its derivative transactions on the basis of its relationships at the counterparty portfolio level. Management receives reports from an independent third-party valuation specialist on a monthly basis providing the credit valuation adjustments at the counterparty portfolio level for purposes of reviewing and managing its credit risk exposures. Since the portfolio exception applies only to the fair value measurement and not to financial statement presentation, the portfolio-level adjustments are then allocated in a reasonable and consistent manner each period to the individual assets or liabilities that make up the group, in accordance with other applicable accounting guidance and the Company's accounting policy elections. Although MBS have characteristics that meet the definition of a derivative instrument, ASC 815 specifically excludes these instruments from its scope because they are accounted for as debt securities under ASC 320.
Interest Income, Premium Amortization, and Discount Accretion [Policy Text Block]	Interest Income, Premium Amortization, and Discount Accretion. Interest income on MBS is accrued based on the outstanding principal balance (or notional balance in the case of interest-only, or "IO", securities) and their contractual terms. Premiums and discounts on Agency MBS as well as any non-Agency MBS rated AA and higher at the time of purchase are amortized into interest income over the expected life of such securities using the effective yield method and adjustments to premium amortization are made for actual prepayment activity as well as changes in projected future cash flows in accordance with ASC Topic 310-20. The Company's projections of future cash flows are based on input and analysis received from external sources and internal models, and includes assumptions about the amount and timing of credit losses, loan prepayment rates, fluctuations in interest rates, and other factors. On at least a quarterly basis, the Company reviews and makes any necessary adjustments to its cash flow projections and updates the yield recognized on these assets. The Company has purchased non-Agency MBS rated less than 'AA' by at least one national rating agency at discounts to their par value, and management does not believe these discounts to be substantial. The Company records the discount accretion into income over the security's expected life, which reflects management's estimate of the security's projected cash flows in accordance with ASC Topic 325-40. Future changes in projected cash flows or differences arising between projected cash flows and actual cash flows received may result in a prospective change in the effective yield on those securities. The accrual of interest on MBS is discontinued when, in the opinion of management, it is probable that all amounts contractually due will not be collected, and in certain instances, as a result of an other-than-temporary impairment analysis ("OTTI", see discussion below). All interest accrued but not collected for investments that are placed on a non-accrual status or are charged-off is reversed against interest income. Interest on these investments is accounted for on the cash-basis or cost-recovery method until the affected investment or investments qualify for return to accrual status. Investments are returned to accrual status when all the principal and interest amounts contractually due are brought current and future payments are reasonably assured.
Stock-based Compensation [Policy Text Block]	Stock-Based Compensation Pursuant to the Company’s 2009 Stock and Incentive Plan ("SIP"), the Company may grant stock-based compensation to eligible employees, directors or consultants or advisers to the Company, including stock awards, stock options, stock appreciation rights (“SARs”), dividend equivalent rights, performance shares, and restricted stock units. Currently, the Company's stock options and restricted stock issued under this plan may be settled only in shares of its common stock, and therefore are treated as equity awards with their fair value measured at the grant date as required by ASC Topic 718. Outstanding SARs issued by the Company may be settled only in cash, and therefore have been treated as liability awards with their fair value estimated at the grant date and remeasured at the end of each reporting period using the Black-Scholes option valuation model as required by ASC Topic 718. Please see Note 10 for additional disclosures regarding the Company's SIP.
Contingencies [Policy Text Block]	Contingencies In the normal course of business, there are various lawsuits, claims, and other contingencies pending against the Company. We evaluate whether to establish provisions for estimated losses from those matters in accordance with ASC Topic 450, which states that a liability is recognized for a contingent loss when: (a) the underlying causal event has occurred prior to the balance sheet date; (b) it is probable that a loss has been incurred; and (c) there is a reasonable basis for estimating that loss. A liability is not recognized for a contingent loss when it is only possible or remotely possible that a loss has been incurred, however, possible contingent losses shall be disclosed. Please refer to Note 12 for details on the most significant matters currently pending.
Description of New Accounting Pronouncements Not yet Adopted [Text Block]	Recent Accounting Pronouncements In July 2013, the FASB issued ASU 2013-10, Derivatives and Hedging (Topic 815), Inclusion of the Fed Funds Effective Swap Rate (or Overnight Index Swap Rate) as a Benchmark Interest Rate for Hedge Accounting Purposes(a consensus of the FASB Emerging Issues Task Force) ("ASU 2013-10"). The new guidance permits the use of the Federal Funds Effective Swap Rate as a benchmark interest rate for hedge accounting purposes and removes certain restrictions on being able to apply hedge accounting for similar hedges using different benchmark interest rates. ASU 2013-10 is effective prospectively for qualifying new or re-designated hedging relationships entered into on or after July 17, 2013. The adoption of this ASU does not have an impact on our derivatives and will not have a material impact on the Company's consolidated financial statements. In June 2013, the FASB issued ASU 2013-08, Financial Services - Investment Companies: Amendments to the Scope, Measurement, and Disclosure Requirements ("ASU 2013-08"). In general, the amendments of this ASU: (i) revise the definition of an investment company; (ii) require an investment company to measure non-controlling ownership interests in other investment companies at fair value rather than using the equity method of accounting; and (iii) require information to be disclosed concerning the status of the entity and any financial support provided, or contractually required to be provided, by the investment company to its investees. ASU 2013-08 is effective for interim and annual periods that begin after December 15, 2013 and early application is prohibited. As the FASB has decided to retain the current U.S. GAAP scope exception from investment company accounting and financial reporting for real estate investment trusts, the adoption of this ASU will not have a material impact on the Company's consolidated financial statements