• recoveries or additional declines in fair value subsequent to the balance sheet date. 

To the extent the Company estimates future expected cash flows, the Company considered all available information in developing those expected cash flows. For asset-backed securities such as pooled trust preferred securities, such information generally includes: 

• remaining payment terms of the security (including as applicable, terms that require underlying obligor payments to increase in the future); 

• current delinquencies and nonperforming assets of underlying collateral; 

• expected future default rates; and 

• subordination levels or other credit enhancements. 

## Agency obligations 

The unrealized losses associated with agency obligations are primarily driven by changes in interest rates and not due to the credit quality of the securities. These securities are issued by U.S. government agencies or government-sponsored entities and do not have any credit losses given the explicit or implicit government guarantee. 

## Agency residential mortgage-backed securities (“RMBS”) 

The unrealized losses associated with Agency RMBS are primarily driven by changes in interest rates and not due to the credit quality of the securities. These securities are issued by U.S. government agencies or government-sponsored entities and do not have any credit losses given the explicit or implicit government guarantee. 

## Securities of U.S. states and political subdivisions 

The unrealized losses associated with securities of U.S. states and political subdivisions are primarily driven by changes in interest rates and are not due to the credit quality of the securities. These securities will continue to be monitored as part of the Company’s quarterly impairment analysis, but are expected to perform even if the rating agencies reduce the credit rating of the bond insurers. As a result, the Company expects to recover the entire amortized cost basis of these securities. 

## Pooled trust preferred securities 

The unrealized losses associated with pooled trust preferred securities are primarily driven by higher projected collateral losses and wider credit spreads. Pooled trust preferred securities primarily consist of securities issued by community banks and thrifts. The Company assesses impairment for these securities using a cash flow model. The key assumptions include default probabilities of the underlying collateral and recoveries on collateral defaults. Based upon the Company’s assessment of the expected credit losses for these securities, and given the performance of the underlying collateral compared to the Company’s credit enhancement, the Company expects to recover the remaining amortized cost basis of these securities. 

## Individual issuer trust preferred securities 

The unrealized losses associated with individual issuer trust preferred securities are primarily related to securities backed by individual issuer community banks. For individual issuers, management evaluates the financial performance of the issuer on a quarterly basis to determine if it is probable that the issuer can make all contractual principal and interest payments. Based upon its evaluation, the Company expects to recover the remaining amortized cost basis of these securities. 

## Cost-method investments 

At December 31, 2011, cost-method investments with an aggregate cost of $5.0 million were not evaluated for impairment because the Company did not identify any events or changes in circumstances that may have a significant adverse effect on the fair value of these cost-method investments. 

The carrying values of the Company’s investment securities could decline in the future if the underlying performance of the collateral for pooled trust preferred securities, the financial condition of individual issuers of trust preferred securities, or the credit quality of other securities deteriorate and the Company determines it is probable that it will not recover the entire amortized cost basis for the security. As a result, there is a risk that significant other-than-temporary impairment charges may occur in the future. 

