Securities with an amortized cost of $288.6 million and $353.8 million at September 30, 2020 and December 31, 2019, respectively, were pledged to secure public deposits and for other purposes.

The Bank, as a member of the Federal Home Loan Bank of Atlanta (“FHLB”), is required to own capital stock in the FHLB based generally upon the balances of residential and commercial real estate loans and FHLB advances. FHLB stock, which is included in equity securities, is pledged to secure FHLB advances. No ready market exists for this stock, and it has no quoted market value; however, redemption of this stock has historically been at par value.

As a member of the Federal Reserve Bank of Atlanta, the Bank is required to maintain stock in the Federal Reserve Bank of Atlanta based on a specified ratio relative to the Bank’s capital. Federal Reserve Bank stock is carried at cost.

Maturity Distribution. At September 30, 2020, the Company's investment securities had the following maturity distribution based on contractual maturity. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations. Mortgage-backed securities and certain amortizing U.S. government agency securities are shown separately because they are not due at a certain maturity date.

Credit Quality Indicators

The Company monitors the credit quality of its investment securities through various risk management procedures, including the monitoring of credit ratings. A majority of the debt securities in the Company’s investment portfolio were issued by a U.S. government entity or agency and are either explicitly or implicitly guaranteed by the U.S. government. The Company believes the long history of no credit losses on these securities indicates that the expectation of nonpayment of the amortized cost basis is zero, even if the U.S. government were to technically default. Further, certain municipal securities held by the Company have been pre-refunded and secured by government guaranteed treasuries. Therefore, for the aforementioned securities, the Company does not assess or record expected credit losses due to the zero loss assumption. The Company monitors the credit quality of its municipal securities portfolio via credit ratings which are updated on a quarterly basis. On a quarterly basis, municipal securities in an unrealized loss position are evaluated to determine if the loss is attributable to credit related factors and if an allowance for credit loss is needed.