prepayments. If the actual and estimated 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.
At the time we purchase CRT securities and non-Agency MBS that are not of high credit quality, we determine an effective yield based on our estimate of the timing and amount of future cash flows and our cost basis. Our initial cash flow estimates for these investments are based on our observations of current information and events and include assumptions related to interest rates, prepayment rates and the impact of default and severity rates on the timing and amount of credit losses. On at least a quarterly basis, we review the estimated cash flows and make appropriate adjustments, based on inputs and analysis received from external sources, internal models, and our judgment regarding such inputs and other factors. Any resulting changes in effective yield are recognized prospectively based on the current amortized cost of the investment as adjusted for credit impairment, if any.
We finance the acquisition of securities for our investment portfolio primarily through repurchase transactions under master repurchase agreements. Pursuant to ASC Topic 860, Transfers and Servicing ("ASC 860"), we account for repurchase transactions as collateralized financing transactions, which are carried at their contractual amounts (cost), plus accrued interest. Our repurchase agreements typically have maturities of less than one year, but may extend up to five years or more. Interest rates on our repurchase agreements generally correspond to one, three or six month LIBOR plus or minus a fixed spread. The fair value of our repurchase agreements is assumed to equal cost as the interest rates are considered to be at market.
Reverse Repurchase Agreements and Obligation to Return Securities Borrowed under Reverse Repurchase Agreements
We borrow securities to cover short sales of U.S. Treasury securities through reverse repurchase transactions under our master repurchase agreements (see Derivative Instruments below). 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. Our reverse repurchase agreements typically have maturities of 30 days or less. The fair value of our reverse repurchase agreements is assumed to equal cost as the interest rates are generally reset daily.
We use a variety of derivative instruments to hedge a portion of our exposure to market risks, including interest rate, prepayment, extension and liquidity risks. The objective of our risk management strategy is to reduce fluctuations in net book value over a range of interest rate scenarios. 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 primary instruments that we use are interest rate swaps, options to enter into interest rate swaps ("swaptions"), U.S. Treasury securities and U.S. Treasury futures contracts. We also use forward contracts in the Agency RMBS "to-be-announced" market ("TBA") to invest in and finance Agency securities as well as to periodically reduce our exposure to Agency RMBS.
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 our accompanying consolidated balance sheets and to measure those instruments at fair value.
Our derivative agreements generally contain provisions that allow for netting or setting off derivative assets and liabilities with the counterparty; however, we report related assets and liabilities on a gross basis in our consolidated balance sheets. Derivative instruments in a gain position are reported as derivative assets at fair value and derivative instruments in a loss position are reported as derivative liabilities at fair value in our consolidated balance sheets. Changes in fair value of derivative instruments and periodic settlements related to our derivative instruments are recorded in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income. Cash receipts and payments related to derivative instruments are classified in our consolidated statements of cash flows according to the underlying nature or purpose of the derivative transaction, generally in the investing section.
The use of derivative instruments creates exposure to credit risk relating to potential losses that could be recognized if the counterparties to these instruments fail to perform their obligations under the contracts. Our derivative agreements require that we post or receive collateral to mitigate such risk. We also attempt to minimize our risk of loss by limiting our counterparties to major financial institutions with acceptable credit ratings, monitoring positions with individual counterparties and adjusting posted collateral as required.