The following table presents the amortized cost and fair value of debt securities as of March 31, 2021 by contractual maturity:

Gross unrealized losses and fair values aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position were as follows at March 31, 2021:

As of March 31, 2021, all securities were investment grade, with credit ratings of AA+ or higher by S&P. Unrealized losses on investment grade securities are principally related to changes in interest rates or changes in issuer or sector related credit spreads since the securities were acquired. The gross unrealized investment losses as of March 31, 2021, were deemed to be temporary, based on, among other things:

The Corporation may ultimately record a realized loss after having originally concluded that the decline in value was temporary. Risks and uncertainties are inherent in the methodology the Corporation uses to assess other-than-temporary declines in value. Risks and uncertainties could include, but are not limited to, incorrect assumptions about financial condition, liquidity or future prospects, inadequacy of any underlying collateral, and unfavorable changes in economic conditions or social trends, interest rates or credit ratings.

Proceeds from sales and maturities of investment securities and related gross realized gains (losses), which are included within other income in the Condensed Consolidated Statements of Operations and Comprehensive Loss, were as follows for the three months ended March 31, 2021 and 2020, respectively:

As of March 31, 2021 and December 31, 2020, the Corporation had $7.5 million and $7.5 million, respectively, in deposits with various states and regulatory bodies that are included as part of the Corporation’s investment balances.

The following tables present the amortized cost and fair value of debt securities as of December 31, 2020, by contractual maturity:

The Corporation has a process in place to identify securities that could potentially have an impairment that is other-than-temporary. This process involves monitoring market events that could impact issuers’ credit ratings, business climate, management changes, litigation and government actions, and other similar factors. This process also involves monitoring late payments, downgrades by rating agencies, key financial ratios, financial statements, revenue forecasts and cash flow projections as indicators of credit issues.

There was an immaterial amount of investment securities in an unrealized loss position as of December 31, 2020 and no investment securities in an unrealized loss position as of December 31, 2019.

As of December 31, 2020 and 2019, all securities were investment grade, with credit ratings of AA+ or higher by S&P. Unrealized losses on investment grade securities are principally related to changes in interest rates or changes in issuer or sector related credit spreads since the securities were acquired.

Proceeds from sales and maturities of investment securities and related gross realized gains (losses) included within net investment income were as follows for the years ended December 31, 2020 and 2019, respectively:

As of December 31, 2020 and 2019, the Corporation had $7.5 million and $3.7 million, respectively, in deposits with various states and regulatory bodies.