fixed maturity portfolio invested in callable agencies, we have reallocated a significant portion of our fixed maturities from the callable agency securities to other highly rated, long-term securities. The largest portion of our fixed maturity securities are now in investment grade (NAIC designation 1 or 2) publicly traded or privately placed corporate securities. We have also built a portfolio of residential mortgage backed securities ("RMBS") that provide our investment portfolio a source of regular cash flow and higher yielding assets than our agency securities. Additionally, in 2009 we began building a portfolio of taxable bonds issued by municipalities, states and territories of the United States that provide us with attractive yields while consistent with our aversion to credit risk.
The fair value of our derivative instruments, including derivative instruments embedded in fixed index annuity contracts, presented in the consolidated balance sheets are as follows:
Our convertible notes are senior unsecured obligations and rank equally in the right of payment with all existing and future senior indebtedness and senior to any existing and future subordinated indebtedness. Our convertible notes effectively rank junior in the right of payment to any existing and future secured indebtedness to the extent of the value of the assets securing such secured indebtedness. Our convertible notes are structurally subordinated to all liabilities of our subsidiaries.
On August 20, 2009, we entered into distribution agreements with Fox-Pitt Kelton Cochran Caronia Waller (USA) LLC (“FPK”) and Sandler O’Neill & Partners, L.P. ("Sandler O'Neill") to offer and sell shares of our common stock up to an aggregate offering price of $50 million. On December 3, 2009, Macquarie Capital (USA) Inc. ("Macquarie Capital") assumed all of FPK's rights and obligations under our distribution
We validate external valuations at least quarterly through a combination of procedures that include the evaluation of methodologies used by the pricing services, analytical reviews and performance analysis of the prices against trends, and maintenance of a securities watch list. Additionally, as needed we utilize discounted cash flow models or perform independent valuations on a case-by-case basis of inputs and assumptions similar to those used by the pricing services. Although we do identify differences from time to time as a result of these validation procedures, we did not make any significant adjustments during the years ended December 31, 2010 and 2009.
We determine whether other than temporary impairment losses should be recognized for debt and equity securities by assessing all facts and circumstances surrounding each security. Where the decline in market value of debt securities is attributable to changes in market interest rates or to factors such as market volatility, liquidity and spread widening, and we anticipate recovery of all contractual or expected cash flows, we do not consider these investments to be other than temporarily impaired because we do not intend to sell these investments and it is not more likely than not we will be required to sell these investments before a recovery of amortized cost, which may be maturity. For equity securities, we recognize an impairment charge in the period in which we do not have the intent and ability to hold the securities until recovery of cost or we determine that the security will not recover to book value within a reasonable period of time. We determine what constitutes a reasonable period of time on a security-by-security basis by considering all the evidence available to us, including the magnitude of any unrealized loss and its duration. In any event, this period does not exceed 18 months from the date of impairment for perpetual preferred securities for which there is evidence of deterioration in credit of the issuer and common equity securities. For perpetual preferred securities absent evidence of a deterioration in credit of the issuer we apply an impairment model, including an anticipated recovery period, similar to a debt security.