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Fair Value Measurements
12 Months Ended
Dec. 31, 2020
Fair Value Disclosures [Abstract]  
Fair Value Measurements

10. Fair Value Measurements

The following tables summarize the Company’s financial assets measured at fair value on a recurring basis as of December 31, 2020 and 2019 and by level within the fair value hierarchy:

Fair value measurement as of December 31, 2020:

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

Quoted prices in

​

Significant other

​

Significant

Financial assets

​

​

​

​

active markets for

​

observable

​

unobservable

​

​

​

​

​

identical assets

​

inputs

​

inputs

Type of Instrument

    

Total

    

(Level 1)

    

(Level 2)

    

(Level 3)

Cash and cash equivalents:

 

​

  

 

​

  

 

​

  

 

​

  

Money market funds and checking accounts

​

$

31,683

​

$

31,683

​

$

—

​

$

—

Available-for-sale marketable securities:

​

 

  

​

 

  

​

 

  

​

 

  

U.S. Treasury securities

​

 

20,750

​

 

—

​

 

20,750

​

 

—

U.S. government agency obligations

​

 

22,128

​

 

—

​

 

22,128

​

 

—

Corporate bonds

​

 

49,118

​

 

—

​

 

49,118

​

 

—

Commercial paper

​

 

116,127

​

 

—

​

 

116,127

​

 

—

Municipal bonds

​

 

11,684

​

 

—

​

 

11,684

​

 

—

Restricted cash:

​

 

​

​

 

  

​

 

  

​

 

  

Commercial money market account

​

 

408

​

 

408

​

 

—

​

 

—

Total financial assets

​

$

251,898

​

$

32,091

​

$

219,807

​

$

—

​

Fair value measurement as of December 31, 2019:

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

Quoted prices in

​

Significant other

​

Significant

Financial assets

​

​

​

​

active markets for

​

observable

​

unobservable

​

​

​

​

​

identical assets

​

inputs

​

inputs

Type of Instrument

    

Total

    

(Level 1)

    

(Level 2)

    

(Level 3)

Cash and cash equivalents:

 

​

  

 

​

  

 

​

  

 

​

  

Money market funds and checking accounts

​

$

18,305

​

$

18,305

​

$

—

​

$

—

Available-for-sale marketable securities:

​

 

  

​

 

  

​

 

  

​

 

  

U.S. Treasury securities

​

​

16,081

​

​

—

​

​

16,081

​

​

—

U.S. government agency obligations

​

 

25,816

​

 

—

​

 

25,816

​

 

—

Corporate bonds

​

 

115,890

​

 

—

​

 

115,890

​

 

—

Commercial paper

​

 

38,573

​

 

—

​

 

38,573

​

 

—

Municipal bonds

​

​

3,500

​

​

—

​

​

3,500

​

​

—

Restricted cash:

​

 

  

​

 

  

​

 

  

​

 

  

Commercial money market account

​

 

408

​

 

408

​

 

—

​

 

—

Total financial assets

​

$

218,573

​

$

18,713

​

$

199,860

​

$

—

​

There were no purchases, sales or maturities of Level 3 financial assets and no unrealized gains or losses related to Level 3 available-for-sale marketable securities for the years ended December 31, 2020, 2019 and 2018. There were no transfers of financial assets between Levels 1, 2, or 3 classifications during the years ended December 31, 2020 and 2019.