Restricted cash

[Table of Contents](#ie5b53d08516744208c4d15ed88453ce2_7)financial institutions and highly liquid investments in money market funds. Interest is accrued as earned. As of December 31, 2021 and 2020, we had restricted cash of $4.2 million, respectively, and that primarily included $4.0 million pledged as collateral representing a security deposit required for a facility lease. Our restricted cash is classified as other assets in the accompanying consolidated balance sheets. Marketable SecuritiesWe classify all highly liquid investments in debt and equity securities with maturities of greater than three months at the date of purchase as marketable securities. We have classified and accounted for our marketable securities as available-for-sale. We determine the appropriate classification of these investments at the time of purchase and reevaluate such designation at each balance sheet date. We may or may not hold securities with stated maturities greater than 12 months until maturity. After consideration of our risk versus reward objectives, as well as our liquidity requirements, we may sell these securities prior to their stated maturities. As we view these securities as available to support current operations, we classify securities with maturities beyond 12 months as current assets under the caption marketable securities in the accompanying consolidated balance sheets. We carry these securities at fair value, and report the unrealized gains and losses, net of taxes, as a component of stockholders’ equity. We determine the cost of the debt investment sold based on an average cost basis at the individual security level, and record the interest income in other income, net in the accompanying consolidated statements of operations. We determine any realized gains or losses on the sale of marketable securities using the specific identification method, and record such gains and losses in other income, net in the accompanying consolidated statements of operations.For our debt securities in an unrealized loss position, we determine whether a credit loss exists by considering information about the collectability of the instrument and current market conditions. We recognize an allowance for credit losses, up to the amount of the unrealized loss when appropriate, and write down the amortized cost basis of the investment if it is more likely than not we will be required to sell or we intend to sell the investment before recovery of its amortized cost basis. Accounts ReceivableAccounts receivable are recorded at the invoiced amount, net of allowances for doubtful accounts, sales rebates and returns reserves. We estimate our allowance for doubtful accounts based upon the collectability of the receivables in light of historical trends, reasonable and supportable information of our customers' economic conditions that may affect our customers’ ability to pay, and prevailing economic conditions. This evaluation is done in order to identify issues that may impact the collectability of receivables and related estimated required allowance. Revisions to the allowance are recorded as an adjustment to bad debt expense. After appropriate collection efforts are exhausted, specific accounts receivable deemed to be uncollectible are charged against the allowance in the period they are deemed uncollectible. Recoveries of accounts receivable previously written-off are recorded as credits to bad debt expense. We primarily estimate our sales rebates and returns reserves based on historical rates applied against current period billings. Specific customer returns, rebates and allowances are considered when determining our estimates. Revisions to sales rebate and return reserves are recorded as adjustments to revenue. Fair Value MeasurementsFair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. We apply fair value accounting for all financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis. These assets and liabilities include cash and cash equivalents, marketable securities, accounts receivable, accounts payable, and accrued liabilities. Cash equivalents, accounts receivable, accounts payable and accrued liabilities are stated at carrying values in our consolidated financial statements, which approximate their fair value due to the short-term nature of these instruments. Assets and liabilities recorded at fair value on a recurring basis in the accompanying consolidated balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their 74
