Summary of Significant Accounting Policies (Policy)	6 Months Ended
Jun. 30, 2011
Summary of Significant Accounting Policies
Investments in Agency Securities	*Investments in Agency Securities* Accounting Standards Codification ("ASC") Topic 320, Investments—Debt and Equity Securities ("ASC 320"), requires that at the time of purchase, we designate a security as held-to-maturity, available-for-sale or trading, depending on our ability and intent to hold such security to maturity. Securities classified as trading and available-for-sale are reported at fair value, while securities classified as held-to-maturity are reported at amortized cost. We may, from time to time, sell any of our agency securities as part of our overall management of our investment portfolio. Accordingly, we typically designate our agency securities as available-for-sale. All securities classified as available-for-sale are reported at fair value, with unrealized gains and losses reported in other comprehensive income (loss) ("OCI"), a component of stockholders' equity. Upon the sale of a security, we determine the cost of the security and the amount of unrealized gains or losses to reclassify out of accumulated OCI into earnings based on the specific identification method. Interest-only securities and inverse interest-only securities (collectively referred to as "interest-only securities") represent our right to receive a specified proportion of the contractual interest flows of specific agency and CMO securities. Principal-only securities represent our right to receive the contractual principal flows of specific agency and CMO securities. Interest-only and principal-only securities are measured at fair value through earnings in gain (loss) on derivative instruments and trading securities, net in our consolidated statements of operations and comprehensive income. Our investments in interest-only and principal only securities are included in agency securities, at fair value on the accompanying consolidated balance sheets. We estimate the fair value of our agency securities based on a market approach using Level 2 inputs from third-party pricing services and dealer quotes. The third-party pricing services use pricing models that incorporate such factors as coupons, primary and secondary mortgage rates, prepayment speeds, spread to the Treasury and interest rate swap curves, convexity, duration, periodic and life caps and credit enhancements. The dealer quotes incorporate common market pricing methods, including a spread measurement to the Treasury or interest rate swap curve as well as underlying characteristics of the particular security including coupon, periodic and life caps, rate reset period, issuer, additional credit support and expected life of the security. We evaluate securities for other-than-temporary impairment ("OTTI") on at least a quarterly basis, and more frequently when economic or market conditions warrant such evaluation. Based on the criteria in ASC 320, the determination of whether a security is other-than-temporarily impaired involves judgments and assumptions based on subjective and objective factors. When an agency security is impaired, an OTTI is considered to have occurred if (i) we intend to sell the agency security (i.e. a decision has been made as the reporting date) or (ii) it is more likely than not that we will be required to sell the agency security before recovery of its amortized cost basis. If we intend to sell the security or if it is more likely than not that we will be required to sell the agency security before recovery of its amortized cost basis, the entire amount of the impairment loss, if any, is recognized in earnings as a realized loss and the cost basis of the security is adjusted to its fair value. We did not recognize any OTTI charges on any of our agency securities for six months ended June 30, 2011 and 2010.
Interest Income	*Interest Income* Interest income is accrued based on the outstanding principal amount of the agency securities and their contractual terms. Premiums and discounts associated with the purchase of agency securities are amortized or accreted into interest income over the projected lives of the securities, including contractual payments and estimated prepayments using the interest method in accordance with ASC Subtopic 310-20, Receivables—Nonrefundable Fees and Other Costs ("ASC 310-20"). We estimate long-term prepayment speeds using a third-party service and market data. The third-party service estimates prepayment speeds using models that incorporate the forward yield curve, current mortgage rates, current mortgage rates of the outstanding loans, loan age, volatility and other factors. We review the prepayment speeds estimated by the third-party service and compare the results to market consensus prepayment speeds, if available. We also consider historical prepayment speeds and current market conditions to validate the reasonableness of the prepayment speeds estimated by the third-party service and based on our Manager's judgment we may make adjustments to their estimates. Actual and anticipated prepayment experience is reviewed quarterly and effective yields are recalculated when differences arise between the previously estimated future prepayments and the amounts actually received plus current anticipated future prepayments. If the actual and anticipated future prepayment experience differs from our prior estimate of prepayments, we are required to record an adjustment in the current period to the amortization or accretion of premiums and discounts for the cumulative difference in the effective yield through the reporting date. In addition, pursuant to ASC 310-20, the yield on our adjustable rate securities assumes that the securities reset at a rate equal to the underlying index rate in effect as of the date we acquired the security plus the stated margin. Consequently, future reset rate assumptions incorporated in our asset yields may differ materially from future reset rates implied by the forward yield curve and the actual reset rates ultimately achieved. Further, notwithstanding changes to our actual and projected constant prepayment rate ("CPR") assumptions, the lower our reset rate assumption is pursuant to ASC 310-20 than the current fixed rate in effect, the greater the rate of premium amortization we will recognize over the initial fixed rate period. Our adjustable rate portfolio was acquired for a premium above par value and most securities were acquired during a period of historically low index rates. Accordingly, the majority of the premium balance on our adjustable rate securities will be amortized prior to their first reset date, regardless of actual or forecasted prepayment speeds and changes in the underlying index rates prior to actual reset. Adjustable rate securities acquired during a different interest rate environment may experience a different premium amortization pattern even as current index rates remain near their historical lows.
Derivative and other Hedging Instruments	*Derivative and other Hedging Instruments* We maintain a risk management strategy, under which we use a variety of strategies to hedge some of our exposure to interest rate risk. The objective of our risk management strategy is to reduce fluctuations in book value and generate additional income distributable to stockholders. In particular, we attempt to mitigate the risk of the cost of our variable rate liabilities increasing during a period of rising interest rates. The principal instruments that we use are interest rate swaps and options to enter into interest rate swaps ("interest rate swaptions"). We also purchase or sell to-be-announced forward contracts ("TBAs"), forward contracts for specified agency securities, U.S. Treasury securities and U.S. Treasury futures contracts, purchase or write put or call options on TBA securities and invest in other types of mortgage derivatives, such as interest-only securities, and synthetic total return swaps, such as the Markit IOS Synthetic Total Return Swap Index ("Markit IOS Index"). We account for derivative instruments in accordance with ASC Topic 815, Derivatives and Hedging ("ASC 815"). ASC 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. Hedging instruments that are not derivatives under ASC 815 are accounted for in accordance with ASC 320. The accounting for changes in the fair value of derivatives depends on the intended use of the derivative and the resulting designation. Derivatives that are intended to hedge exposure to variability in expected future cash flows are considered cash flow hedges. For derivatives designated in qualifying cash flow hedging relationships, the effective portion of the fair value adjustments is initially recorded in OCI (a component of stockholders' equity) and reclassified to income at the time that the hedged transactions affect earnings. The ineffective portion of the fair value adjustments is immediately recognized in gain (loss) on derivative instruments and trading securities, net. When the underlying hedged transaction ceases to exist, any amounts that have been previously recorded in accumulated OCI would be reclassified to net income and all subsequent changes in the fair value of the instrument would be included in gain (loss) on derivative instruments and trading securities, net for each period until the derivative instrument matures or is settled. For derivatives not designated in hedging relationships under ASC 815, the fair value adjustments are recorded in gain (loss) on derivative instruments and trading securities, net. Derivatives in a gain position are reported as derivative assets at fair value and derivatives in a loss position are reported as derivative liabilities at fair value in our consolidated balance sheets. In our consolidated statements of cash flows, cash receipts and payments related to derivative instruments are classified according to the underlying nature or purpose of the derivative transaction, generally in the operating section for derivatives designated in hedging relationships and the investing section for derivatives not designated in hedging relationships. The use of derivatives creates exposure to credit risk relating to potential losses that could be recognized in the event that the counterparties to these instruments fail to perform their obligations under the contracts. We attempt to minimize this risk by limiting our counterparties to major financial institutions with acceptable credit ratings and monitoring positions with individual counterparties. Interest rate swap agreements We use interest rate swaps to hedge the variable cash flows associated with short-term borrowings made under our repurchase agreement facilities. We generally enter into such derivatives with the intention of qualifying for hedge accounting under ASC 815. We estimate the fair value of interest rate swaps based on inputs from a third-party pricing model. The third-party pricing model incorporates such factors as the Treasury curve, LIBOR rates, and the pay rate on the interest rate swaps. We also incorporate both our own and our counterparties' nonperformance risk in estimating the fair value of our interest rate swap and swaption agreements. In considering the effect of nonperformance risk, we consider the impact of netting and credit enhancements, such as collateral postings and guarantees, and have concluded that our own and our counterparty risk is not significant to the overall valuation of these agreements. Interest rate swaptions We may purchase interest rate swaptions to help mitigate the potential impact of increases or decreases in interest rates on the performance of our investment portfolio (referred to as "convexity risk"). The interest rate swaptions provide us the option to enter into an interest rate swap agreement for a predetermined notional amount, stated term and pay and receive interest rates in the future. The premium paid for interest rate swaptions is reported as an asset in our consolidated balance sheets. The premium is valued at an amount equal to the fair value of the swaption that would have the effect of closing the position adjusted for nonperformance risk, if any. The difference between the premium and the fair value of the swaption is reported in gain (loss) on derivative instruments and trading securities, net in our consolidated statement of operations and comprehensive income. If a swaption expires unexercised, the loss on the swaption would be equal to the premium paid. If we sell or exercise a swaption, the realized gain or loss on the swaption would be equal to the difference between the cash or the fair value of the underlying interest rate swap received and the premium paid. We estimate the fair value of interest rate swaptions based on the fair value of the future interest rate swap that we have the option to enter into as well as the remaining length of time that we have to exercise the option. TBA securities A TBA security is a futures contract for the purchase or sale of agency securities at a predetermined price, face amount, issuer, coupon and stated maturity on an agreed-upon future date. The specific agency securities delivered into the contract upon the settlement date, published each month by the Securities Industry and Financial Markets Association, are not known at the time of the transaction. TBA securities are exempt from ASC 815 and are accounted for under ASC 320 if there is no other way to purchase or sell that security, if delivery of that security and settlement will occur within the shortest period possible for that type of security and if it is probable at inception and throughout the term of the individual contract that physical delivery of the security will occur (referred to as the "regular-way" exception). Alternatively, we may designate the TBA security as a qualifying cash flow hedge under ASC 815 if the regular-way exception is not met and at the time of the purchase or sale of the security, and throughout the term of the individual contract, it is probable that the forecasted transaction will occur and the hedging relationship is expected to be highly effective. For TBA security contracts that we have entered into, we have generally not asserted that physical settlement is probable or that the forecasted transaction is probable of occurring and, therefore, we typically have not designated these forward commitments as hedging instruments. Realized and unrealized gains and losses associated with TBA contracts not subject to the regular-way exception or not designated as hedging instruments are recognized in our consolidated statement of operations and comprehensive income in the line item gain (loss) on derivative instruments and trading securities, net. We estimate the fair value of TBA securities based on similar methods used to value agency securities. Put and call options on TBA securities We may purchase put and call options on TBA securities to hedge against short-term changes in interest rates. Under a purchased put option, we have the right to sell to the counterparty a specified TBA security at a predetermined price on the option exercise date in exchange for a premium at execution. Under a purchased call option, we have the right to purchase from the counterparty a specified TBA security at a predetermined price on the option exercise date in exchange for a premium at execution. The premium paid for a put or call option is reported as an asset in our consolidated balance sheets. The premium is valued at an amount equal to the fair value of the option that would have the effect of closing the position adjusted for nonperformance risk, if any. The difference between the premium and the fair value of the option is reported in gain (loss) on derivative instruments and trading securities, net in our consolidated statement of operations and comprehensive income. When a purchased put or call option expires unexercised, a realized loss is reported in our consolidated statement of operations and comprehensive income equal to the premium paid. When a purchased put or call option is exercised, a realized gain or loss is reported in our consolidated statement of operations and comprehensive income equal to the difference between the premium paid and the fair value of the exercised put or call option. In addition, a derivative asset is recorded in our consolidated balance sheet for the TBA security resulting from the put or call option exercise. We may also write put and call options on TBA securities. Under a written put option, the counterparty has the right to sell us a specified TBA security at a predetermined price on the option exercise date in exchange for a premium at execution. Under a written call option, the counterparty has the right to purchase from us a specified TBA security at a predetermined price on the option exercise date in exchange for a premium at execution. The premium received from writing a put or call option is reported as a liability in our consolidated balance sheets. The premium is valued at an amount equal to the fair value of the option that would have the effect of closing the position adjusted for nonperformance risk, if any. The difference between the premium and the fair value of the option is reported in gain (loss) on derivative instruments and trading securities, net in our consolidated statement of operations and comprehensive income. When a written put or call option expires unexercised, a realized gain is reported in our consolidated statement of operations equal to the premium received. When we terminate a written put or call option, a realized gain or loss is reported in our consolidated statement of operations equal to the difference between the termination payment and the premium received. When a written put or call option is exercised, a realized gain or loss is reported in our consolidated statement of operations equal to the difference between the premium received and the fair value of the exercised put or call option. In addition, a derivative asset or liability is recorded in our consolidated balance sheet for the TBA security resulting from the put or call option exercise. We estimate the fair value of put and call options on TBA securities based on the fair value of the underlying TBA security as well as the remaining length of time to exercise the option. Forward commitments to purchase or sell specified agency securities We may enter into a forward commitment to purchase or sell specified agency securities as a means of acquiring assets or as a hedge against short-term changes in interest rates. Contracts for the purchase or sale of specified agency securities are accounted for as derivatives if the delivery of the specified agency security and settlement extends beyond the shortest period possible for that type of security. We may designate the forward commitment as a qualifying cash flow hedge if at the time of the purchase or sale of the security, and throughout the term of the individual contract, it is probable that physical delivery of the security will occur. Realized and unrealized gains and losses associated with forward commitments not designated as hedging instruments are recognized in our consolidated statement of operations and comprehensive income in the line item gain (loss) on derivative instruments and trading securities, net. We estimate the fair value of forward commitments to purchase or sell specified agency securities based on similar methods used to value agency securities as well as the remaining length of time of the forward commitment. U.S. Treasury securities We may purchase or sell short U.S. Treasury securities and U.S. Treasury futures contracts to help mitigate the potential impact of changes in interest rates on the performance of our portfolio. We may borrow securities to cover short sales of U.S. Treasury securities under reverse repurchase agreements. We account for these as securities borrowing transactions and recognize an obligation to return the borrowed securities at fair value on the balance sheet based on the value of the underlying borrowed securities as of the reporting date. Realized and unrealized gains and losses associated with purchases and short sales of U.S Treasury securities are recognized in gains (losses) on derivative instruments and trading securities, net in our consolidated statements of operations and comprehensive income. Total return swaps We may enter into total return swaps to obtain exposure to a security or market sector without owning such security or investing directly in that market sector. Total return swaps are agreements in which there is an exchange of cash flows whereby one party commits to make payments based on the total return (coupon plus the mark-to-market movement) of an underlying instrument or index in exchange for fixed or floating rate interest payments. To the extent the total return of the instrument or index underlying the transaction exceeds or falls short of the offsetting interest rate obligation, we will receive a payment from or make a payment to the counterparty. The primary total return swap index in which we invest is the Markit IOS Index. Total return swaps based on the Markit IOS index are intended to synthetically replicate the performance of interest-only securities. We determine the fair value of our total return swaps based on published index prices. Realized and unrealized gains and losses associated with changes in market value of the underlying index and coupon interest are recognized in gain (loss) on derivative instruments and trading securities, net in our consolidated statements of operations and comprehensive income.
Variable Interest Entities	*Variable Interest Entities* ASC Topic 810, Consolidation ("ASC 810"), requires a qualitative assessment in determining the primary beneficiary of a variable interest entities ("VIEs") and ongoing assessments of control over such entities as well as additional disclosures for entities that have variable interests in VIEs. We may enter into transactions involving a CMO trust (e.g. a VIE) whereby we transfer agency securities to an investment bank in exchange for cash proceeds and at the same time enter into a commitment with the same investment bank to purchase to-be-issued securities collateralized by the agency securities transferred. We will consolidate a CMO trust (as it relates to the assets transferred or contributed by us and the related liabilities issued by the trust) if we are the CMO trust's primary beneficiary; that is, if we have a variable interest (or combination of variable interests) that provides us with a controlling financial interest in the CMO trust. An entity is deemed to have a controlling financial interest if the entity has the power to direct the activities of a VIE that most significantly impacts the VIE's economic performance and the obligation to absorb losses of or right to receive benefits from the VIE that could potentially be significant to the VIE. In determining if we have a controlling financial interest, we evaluate whether we share the power to control the selection of financial assets transferred to the CMO trust with an unrelated party. We may share power in the selection of assets for certain CMO trusts (i.e., both we and the unrelated party must consent to the transfer of such assets to the CMO trust); however, if our economic interest in the CMO trust is disproportionate to the shared power, we may be deemed to be the primary beneficiary.

Summary of Significant Accounting Policies (Policy)

6 Months Ended

Jun. 30, 2011

Summary of Significant Accounting Policies

Investments in Agency Securities

Accounting Standards Codification ("ASC") Topic 320, Investments—Debt and Equity Securities ("ASC 320"), requires that at the time of purchase, we designate a security as held-to-maturity, available-for-sale or trading, depending on our ability and intent to hold such security to maturity. Securities classified as trading and available-for-sale are reported at fair value, while securities classified as held-to-maturity are reported at amortized cost. We may, from time to time, sell any of our agency securities as part of our overall management of our investment portfolio. Accordingly, we typically designate our agency securities as available-for-sale. All securities classified as available-for-sale are reported at fair value, with unrealized gains and losses reported in other comprehensive income (loss) ("OCI"), a component of stockholders' equity. Upon the sale of a security, we determine the cost of the security and the amount of unrealized gains or losses to reclassify out of accumulated OCI into earnings based on the specific identification method.

Interest-only securities and inverse interest-only securities (collectively referred to as "interest-only securities") represent our right to receive a specified proportion of the contractual interest flows of specific agency and CMO securities. Principal-only securities represent our right to receive the contractual principal flows of specific agency and CMO securities. Interest-only and principal-only securities are measured at fair value through earnings in gain (loss) on derivative instruments and trading securities, net in our consolidated statements of operations and comprehensive income. Our investments in interest-only and principal only securities are included in agency securities, at fair value on the accompanying consolidated balance sheets.

We estimate the fair value of our agency securities based on a market approach using Level 2 inputs from third-party pricing services and dealer quotes. The third-party pricing services use pricing models that incorporate such factors as coupons, primary and secondary mortgage rates, prepayment speeds, spread to the Treasury and interest rate swap curves, convexity, duration, periodic and life caps and credit enhancements. The dealer quotes incorporate common market pricing methods, including a spread measurement to the Treasury or interest rate swap curve as well as underlying characteristics of the particular security including coupon, periodic and life caps, rate reset period, issuer, additional credit support and expected life of the security.

We evaluate securities for other-than-temporary impairment ("OTTI") on at least a quarterly basis, and more frequently when economic or market conditions warrant such evaluation. Based on the criteria in ASC 320, the determination of whether a security is other-than-temporarily impaired involves judgments and assumptions based on subjective and objective factors. When an agency security is impaired, an OTTI is considered to have occurred if (i) we intend to sell the agency security (i.e. a decision has been made as the reporting date) or (ii) it is more likely than not that we will be required to sell the agency security before recovery of its amortized cost basis. If we intend to sell the security or if it is more likely than not that we will be required to sell the agency security before recovery of its amortized cost basis, the entire amount of the impairment loss, if any, is recognized in earnings as a realized loss and the cost basis of the security is adjusted to its fair value.

We did not recognize any OTTI charges on any of our agency securities for six months ended June 30, 2011 and 2010.

Interest Income

Interest Income

Interest income is accrued based on the outstanding principal amount of the agency securities and their contractual terms. Premiums and discounts associated with the purchase of agency securities are amortized or accreted into interest income over the projected lives of the securities, including contractual payments and estimated prepayments using the interest method in accordance with ASC Subtopic 310-20, Receivables—Nonrefundable Fees and Other Costs ("ASC 310-20").

We estimate long-term prepayment speeds using a third-party service and market data. The third-party service estimates prepayment speeds using models that incorporate the forward yield curve, current mortgage rates, current mortgage rates of the outstanding loans, loan age, volatility and other factors. We review the prepayment speeds estimated by the third-party service and compare the results to market consensus prepayment speeds, if available. We also consider historical prepayment speeds and current market conditions to validate the reasonableness of the prepayment speeds estimated by the third-party service and based on our Manager's judgment we may make adjustments to their estimates. Actual and anticipated prepayment experience is reviewed quarterly and effective yields are recalculated when differences arise between the previously estimated future prepayments and the amounts actually received plus current anticipated future prepayments. If the actual and anticipated future prepayment experience differs from our prior estimate of prepayments, we are required to record an adjustment in the current period to the amortization or accretion of premiums and discounts for the cumulative difference in the effective yield through the reporting date.

In addition, pursuant to ASC 310-20, the yield on our adjustable rate securities assumes that the securities reset at a rate equal to the underlying index rate in effect as of the date we acquired the security plus the stated margin. Consequently, future reset rate assumptions incorporated in our asset yields may differ materially from future reset rates implied by the forward yield curve and the actual reset rates ultimately achieved. Further, notwithstanding changes to our actual and projected constant prepayment rate ("CPR") assumptions, the lower our reset rate assumption is pursuant to ASC 310-20 than the current fixed rate in effect, the greater the rate of premium amortization we will recognize over the initial fixed rate period.

Our adjustable rate portfolio was acquired for a premium above par value and most securities were acquired during a period of historically low index rates. Accordingly, the majority of the premium balance on our adjustable rate securities will be amortized prior to their first reset date, regardless of actual or forecasted prepayment speeds and changes in the underlying index rates prior to actual reset. Adjustable rate securities acquired during a different interest rate environment may experience a different premium amortization pattern even as current index rates remain near their historical lows.

Derivative and other Hedging Instruments

Derivative and other Hedging Instruments

We maintain a risk management strategy, under which we use a variety of strategies to hedge some of our exposure to interest rate risk. The objective of our risk management strategy is to reduce fluctuations in book value and generate additional income distributable to stockholders. In particular, we attempt to mitigate the risk of the cost of our variable rate liabilities increasing during a period of rising interest rates. The principal instruments that we use are interest rate swaps and options to enter into interest rate swaps ("interest rate swaptions"). We also purchase or sell to-be-announced forward contracts ("TBAs"), forward contracts for specified agency securities, U.S. Treasury securities and U.S. Treasury futures contracts, purchase or write put or call options on TBA securities and invest in other types of mortgage derivatives, such as interest-only securities, and synthetic total return swaps, such as the Markit IOS Synthetic Total Return Swap Index ("Markit IOS Index").

We account for derivative instruments in accordance with ASC Topic 815, Derivatives and Hedging ("ASC 815"). ASC 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. Hedging instruments that are not derivatives under ASC 815 are accounted for in accordance with ASC 320.

The accounting for changes in the fair value of derivatives depends on the intended use of the derivative and the resulting designation. Derivatives that are intended to hedge exposure to variability in expected future cash flows are considered cash flow hedges. For derivatives designated in qualifying cash flow hedging relationships, the effective portion of the fair value adjustments is initially recorded in OCI (a component of stockholders' equity) and reclassified to income at the time that the hedged transactions affect earnings. The ineffective portion of the fair value adjustments is immediately recognized in gain (loss) on derivative instruments and trading securities, net. When the underlying hedged transaction ceases to exist, any amounts that have been previously recorded in accumulated OCI would be reclassified to net income and all subsequent changes in the fair value of the instrument would be included in gain (loss) on derivative instruments and trading securities, net for each period until the derivative instrument matures or is settled. For derivatives not designated in hedging relationships under ASC 815, the fair value adjustments are recorded in gain (loss) on derivative instruments and trading securities, net. Derivatives in a gain position are reported as derivative assets at fair value and derivatives in a loss position are reported as derivative liabilities at fair value in our consolidated balance sheets. In our consolidated statements of cash flows, cash receipts and payments related to derivative instruments are classified according to the underlying nature or purpose of the derivative transaction, generally in the operating section for derivatives designated in hedging relationships and the investing section for derivatives not designated in hedging relationships.

The use of derivatives creates exposure to credit risk relating to potential losses that could be recognized in the event that the counterparties to these instruments fail to perform their obligations under the contracts. We attempt to minimize this risk by limiting our counterparties to major financial institutions with acceptable credit ratings and monitoring positions with individual counterparties.

Interest rate swap agreements

We use interest rate swaps to hedge the variable cash flows associated with short-term borrowings made under our repurchase agreement facilities. We generally enter into such derivatives with the intention of qualifying for hedge accounting under ASC 815.

We estimate the fair value of interest rate swaps based on inputs from a third-party pricing model. The third-party pricing model incorporates such factors as the Treasury curve, LIBOR rates, and the pay rate on the interest rate swaps. We also incorporate both our own and our counterparties' nonperformance risk in estimating the fair value of our interest rate swap and swaption agreements. In considering the effect of nonperformance risk, we consider the impact of netting and credit enhancements, such as collateral postings and guarantees, and have concluded that our own and our counterparty risk is not significant to the overall valuation of these agreements.

Interest rate swaptions

We may purchase interest rate swaptions to help mitigate the potential impact of increases or decreases in interest rates on the performance of our investment portfolio (referred to as "convexity risk"). The interest rate swaptions provide us the option to enter into an interest rate swap agreement for a predetermined notional amount, stated term and pay and receive interest rates in the future. The premium paid for interest rate swaptions is reported as an asset in our consolidated balance sheets. The premium is valued at an amount equal to the fair value of the swaption that would have the effect of closing the position adjusted for nonperformance risk, if any. The difference between the premium and the fair value of the swaption is reported in gain (loss) on derivative instruments and trading securities, net in our consolidated statement of operations and comprehensive income. If a swaption expires unexercised, the loss on the swaption would be equal to the premium paid. If we sell or exercise a swaption, the realized gain or loss on the swaption would be equal to the difference between the cash or the fair value of the underlying interest rate swap received and the premium paid.

We estimate the fair value of interest rate swaptions based on the fair value of the future interest rate swap that we have the option to enter into as well as the remaining length of time that we have to exercise the option.

TBA securities

A TBA security is a futures contract for the purchase or sale of agency securities at a predetermined price, face amount, issuer, coupon and stated maturity on an agreed-upon future date. The specific agency securities delivered into the contract upon the settlement date, published each month by the Securities Industry and Financial Markets Association, are not known at the time of the transaction. TBA securities are exempt from ASC 815 and are accounted for under ASC 320 if there is no other way to purchase or sell that security, if delivery of that security and settlement will occur within the shortest period possible for that type of security and if it is probable at inception and throughout the term of the individual contract that physical delivery of the security will occur (referred to as the "regular-way" exception). Alternatively, we may designate the TBA security as a qualifying cash flow hedge under ASC 815 if the regular-way exception is not met and at the time of the purchase or sale of the security, and throughout the term of the individual contract, it is probable that the forecasted transaction will occur and the hedging relationship is expected to be highly effective. For TBA security contracts that we have entered into, we have generally not asserted that physical settlement is probable or that the forecasted transaction is probable of occurring and, therefore, we typically have not designated these forward commitments as hedging instruments. Realized and unrealized gains and losses associated with TBA contracts not subject to the regular-way exception or not designated as hedging instruments are recognized in our consolidated statement of operations and comprehensive income in the line item gain (loss) on derivative instruments and trading securities, net.

We estimate the fair value of TBA securities based on similar methods used to value agency securities.

Put and call options on TBA securities

We may purchase put and call options on TBA securities to hedge against short-term changes in interest rates. Under a purchased put option, we have the right to sell to the counterparty a specified TBA security at a predetermined price on the option exercise date in exchange for a premium at execution. Under a purchased call option, we have the right to purchase from the counterparty a specified TBA security at a predetermined price on the option exercise date in exchange for a premium at execution. The premium paid for a put or call option is reported as an asset in our consolidated balance sheets. The premium is valued at an amount equal to the fair value of the option that would have the effect of closing the position adjusted for nonperformance risk, if any. The difference between the premium and the fair value of the option is reported in gain (loss) on derivative instruments and trading securities, net in our consolidated statement of operations and comprehensive income. When a purchased put or call option expires unexercised, a realized loss is reported in our consolidated statement of operations and comprehensive income equal to the premium paid. When a purchased put or call option is exercised, a realized gain or loss is reported in our consolidated statement of operations and comprehensive income equal to the difference between the premium paid and the fair value of the exercised put or call option. In addition, a derivative asset is recorded in our consolidated balance sheet for the TBA security resulting from the put or call option exercise.

We may also write put and call options on TBA securities. Under a written put option, the counterparty has the right to sell us a specified TBA security at a predetermined price on the option exercise date in exchange for a premium at execution. Under a written call option, the counterparty has the right to purchase from us a specified TBA security at a predetermined price on the option exercise date in exchange for a premium at execution. The premium received from writing a put or call option is reported as a liability in our consolidated balance sheets. The premium is valued at an amount equal to the fair value of the option that would have the effect of closing the position adjusted for nonperformance risk, if any. The difference between the premium and the fair value of the option is reported in gain (loss) on derivative instruments and trading securities, net in our consolidated statement of operations and comprehensive income. When a written put or call option expires unexercised, a realized gain is reported in our consolidated statement of operations equal to the premium received. When we terminate a written put or call option, a realized gain or loss is reported in our consolidated statement of operations equal to the difference between the termination payment and the premium received. When a written put or call option is exercised, a realized gain or loss is reported in our consolidated statement of operations equal to the difference between the premium received and the fair value of the exercised put or call option. In addition, a derivative asset or liability is recorded in our consolidated balance sheet for the TBA security resulting from the put or call option exercise.

We estimate the fair value of put and call options on TBA securities based on the fair value of the underlying TBA security as well as the remaining length of time to exercise the option.

Forward commitments to purchase or sell specified agency securities

We may enter into a forward commitment to purchase or sell specified agency securities as a means of acquiring assets or as a hedge against short-term changes in interest rates. Contracts for the purchase or sale of specified agency securities are accounted for as derivatives if the delivery of the specified agency security and settlement extends beyond the shortest period possible for that type of security. We may designate the forward commitment as a qualifying cash flow hedge if at the time of the purchase or sale of the security, and throughout the term of the individual contract, it is probable that physical delivery of the security will occur. Realized and unrealized gains and losses associated with forward commitments not designated as hedging instruments are recognized in our consolidated statement of operations and comprehensive income in the line item gain (loss) on derivative instruments and trading securities, net.

We estimate the fair value of forward commitments to purchase or sell specified agency securities based on similar methods used to value agency securities as well as the remaining length of time of the forward commitment.

U.S. Treasury securities

We may purchase or sell short U.S. Treasury securities and U.S. Treasury futures contracts to help mitigate the potential impact of changes in interest rates on the performance of our portfolio. We may borrow securities to cover short sales of U.S. Treasury securities under reverse repurchase agreements. We account for these as securities borrowing transactions and recognize an obligation to return the borrowed securities at fair value on the balance sheet based on the value of the underlying borrowed securities as of the reporting date. Realized and unrealized gains and losses associated with purchases and short sales of U.S Treasury securities are recognized in gains (losses) on derivative instruments and trading securities, net in our consolidated statements of operations and comprehensive income.

Total return swaps

We may enter into total return swaps to obtain exposure to a security or market sector without owning such security or investing directly in that market sector. Total return swaps are agreements in which there is an exchange of cash flows whereby one party commits to make payments based on the total return (coupon plus the mark-to-market movement) of an underlying instrument or index in exchange for fixed or floating rate interest payments. To the extent the total return of the instrument or index underlying the transaction exceeds or falls short of the offsetting interest rate obligation, we will receive a payment from or make a payment to the counterparty.

The primary total return swap index in which we invest is the Markit IOS Index. Total return swaps based on the Markit IOS index are intended to synthetically replicate the performance of interest-only securities. We determine the fair value of our total return swaps based on published index prices. Realized and unrealized gains and losses associated with changes in market value of the underlying index and coupon interest are recognized in gain (loss) on derivative instruments and trading securities, net in our consolidated statements of operations and comprehensive income.

Variable Interest Entities

Variable Interest Entities

ASC Topic 810, Consolidation ("ASC 810"), requires a qualitative assessment in determining the primary beneficiary of a variable interest entities ("VIEs") and ongoing assessments of control over such entities as well as additional disclosures for entities that have variable interests in VIEs.

We may enter into transactions involving a CMO trust (e.g. a VIE) whereby we transfer agency securities to an investment bank in exchange for cash proceeds and at the same time enter into a commitment with the same investment bank to purchase to-be-issued securities collateralized by the agency securities transferred. We will consolidate a CMO trust (as it relates to the assets transferred or contributed by us and the related liabilities issued by the trust) if we are the CMO trust's primary beneficiary; that is, if we have a variable interest (or combination of variable interests) that provides us with a controlling financial interest in the CMO trust. An entity is deemed to have a controlling financial interest if the entity has the power to direct the activities of a VIE that most significantly impacts the VIE's economic performance and the obligation to absorb losses of or right to receive benefits from the VIE that could potentially be significant to the VIE. In determining if we have a controlling financial interest, we evaluate whether we share the power to control the selection of financial assets transferred to the CMO trust with an unrelated party. We may share power in the selection of assets for certain CMO trusts (i.e., both we and the unrelated party must consent to the transfer of such assets to the CMO trust); however, if our economic interest in the CMO trust is disproportionate to the shared power, we may be deemed to be the primary beneficiary.