We monitor the credit quality of available for sale debt securities through credit ratings from various rating agencies and substantial price changes. Credit ratings express opinions about the credit quality of a security and are utilized us to make informed decisions. Securities are triggered for further review in the quarter if the security has significant fluctuations in ratings, drops below investment grade, or significant pricing changes. For securities without credit ratings, we utilize other financial information indicating the financial health of the underlying municipality, agency, or organization associated with the underlying security.

As of December 31, 2022 and 2021, we carried no allowance on available for sale debt securities in accordance with ASC 326, Measurement of Credit Losses on Financial Instruments.

The amortized cost and estimated fair value of available for sale securities segregated by contractual maturity at December 31, 2022 are presented below. Expected maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations. Mortgage-backed securities are shown in total, as their maturities are highly variable.

The following table summarizes proceeds from the sale of AFS securities and realized gains and losses:

Securities with unrealized losses, segregated by the duration of their continuous unrealized loss positions, are summarized as follows:

A summary of securities pledged as collateral for certain deposits and borrowing arrangements for the years ended December 31, 2022 and 2021 is as follows:

(1)	The Bank pledged securities as collateral for certain borrowing arrangements with the Federal Home Loan Bank of Boston and Federal Reserve Bank of Boston.

We expect to recover the amortized cost basis on all securities in our AFS portfolio. Furthermore, we do not intend to sell nor do we anticipate that we will be required to sell any securities in an unrealized loss position as of December 31, 2022, prior to this recovery. Our ability and intent to hold these securities until recovery is supported by our capital and liquidity positions as well as historically low portfolio turnover.

The following summarizes, by investment security type, the impact of securities in an unrealized loss position for greater than 12 months at December 31, 2022:

US Government-sponsored enterprises

484 out of the total 514 securities in our portfolios of AFS US Government-sponsored enterprises were in unrealized loss positions. Aggregate unrealized losses represented 14.21% of the amortized cost of securities in unrealized loss positions. The FNMA and FHLMC guarantee the contractual cash flows of all of our US Government- sponsored enterprises. The securities are investment grade rated and there were no material underlying credit downgrades during the year. All securities are performing.

US Government agencies

140 out of the total 161 securities in our portfolios of AFS US Government agency securities were in unrealized loss positions. Aggregate unrealized losses represented 12.15% of the amortized cost of securities in unrealized loss positions. The Government National Mortgage Association (“GNMA”) guarantees the contractual cash flows of all of our US government agency securities. The securities are rated investment grade and there were no material underlying credit downgrades during the year. All securities are performing.

Private-label

31 of the total 34 securities in our portfolio of AFS private-label mortgage-backed securities were in unrealized loss positions. Aggregate unrealized losses represented 6.15% of the amortized cost of securities in unrealized loss positions. Based upon the foregoing considerations, and the expectation that our will receive all of the future contractual cash flows related to the amortized cost on these securities, we do not consider there to be any additional other-than-temporary impairment with respect to these securities.

Obligations of states and political subdivisions thereof

67 of the total 77 securities in our portfolio of AFS municipal bonds and obligations were in unrealized loss positions. Aggregate unrealized losses represented 16.96% of the amortized cost of securities in unrealized loss positions. We continually monitor the municipal bond sector of the market carefully and periodically evaluate the appropriate level of exposure to the market. At this time, we believe the bonds in this portfolio carry minimal risk of default and we are appropriately compensated for that risk. There were no material underlying credit downgrades during the year. All securities are performing.

Corporate bonds

30 of the total 33 securities in our portfolio of AFS corporate bonds were in an unrealized loss position. The aggregate unrealized loss represents 8.59% of the amortized cost of securities in unrealized loss positions. We review the financial strength of all of these bonds and have concluded that the amortized cost remains supported by the expected future cash flows of these securities.