Fair Value Measurements	9 Months Ended
	Sep. 30, 2021
Fair Value Measurements [Abstract]
Fair Value Measurements	4.    Fair Value Measurements The Company measures certain financial assets and liabilities at fair value on a recurring basis, including cash equivalents and investments. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or a liability. A three-tier fair value hierarchy is established as a basis for considering such assumptions and for inputs used in the valuation methodologies in measuring fair value: •Level 1 – quoted prices in active markets for identical assets or liabilities; •Level 2 – observable inputs other than quoted prices in active markets for identical assets and liabilities; •Level 3 – unobservable inputs. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. The Company’s cash equivalents are classified within Level 1 of the fair value hierarchy because they are valued using quoted market prices, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency. The corporate bonds/notes, commercial paper, asset-backed securities and U.S. government securities are classified as Level 2 as they are valued based upon quoted market prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active and model-based valuation techniques for which all significant inputs are observable in the market or can be corroborated by observable market data for substantially the full term of the assets. The following tables sets forth by level within the fair value hierarchy the Company’s assets that are reported at fair value as of September 30, 2021 and December 31, 2020, using the inputs defined above (in thousands): September 30, 2021 Level 1 Level 2 Level 3 TotalAssets: Money market funds$ 105,629  $—  $—  $ 105,629 Commercial paper —  2,000  —  2,000 U.S. government securities —  15,127  —  15,127  $ 105,629  $ 17,127  $—  $ 122,756  December 31, 2020 Level 1 Level 2 Level 3 TotalAssets: Money market funds$ 60,295  $—  $—  $ 60,295 Commercial paper —  39,577  —  39,577 Corporate bonds/notes —  7,969  —  7,969 U.S. government securities —  38,470  —  38,470  $ 60,295  $ 86,016  $—  $ 146,311  There were no transfers between fair value hierarchy levels during the three and nine months ended September 30, 2021 and 2020.