In January 2021, we entered into a collaboration framework agreement with Toyota with the intention of deploying the Aurora Driver into a fleet of Toyota Sienna vehicles, subject to further agreement of a collaboration project plan. In April 2021, we received a $50,000 payment from Toyota as a part of this collaboration agreement and it is recorded as a deposit liability pending finalization of the project plan.

Property and equipment consist of the following as of June 30, 2021 and December 31, 2020:

 

Accrued expenses and other current liabilities consist of the following as of June 30, 2021 and December 31, 2020:

 

 

All short-term investments as of December 31, 2019 matured in 2020 and funds were reinvested in highly liquid investments classified as cash equivalents. During fiscal 2020 and 2019, there were no realized gains or losses from sales of marketable securities and there were no reclassifications out of accumulated other comprehensive income into investment income.

The amortized costs, unrealized gains and estimated fair values of the Company’s short-term investments as of December 31, 2019 were as follows

 

 

All securities had stated effective maturities of one year or less.

 

The Company uses a three-level hierarchy, which prioritizes, within the measurement of fair value, the use of market-based information over entity-specific information for fair value measurement based on the nature of inputs used in the valuation of an asset or liability as of the measurement date. Fair value focuses on an exit price and is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The inputs or methodology used for valuing financial instruments are not necessarily an indication of the risk associated with those financial instruments.

The three-level hierarchy for fair value measurements is defined as follows:

An asset or liability’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement.

The following table summarizes the Company’s fair value hierarchy for its financial assets measured at fair value on a recurring bases as of December 31, 2020 and 2019:

 

 

The Company’s marketable security investments are carried at fair value under the Level 1 and 2 valuation hierarchy based on quoted prices in an active market.

 

Property and equipment consist of the following at December 31:

 

 

Other assets consist of the following at December 31:

 

 

Accrued expenses and other current liabilities consist of the following at December 31: