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Fair Value Measurements (Tables)
3 Months Ended
Mar. 31, 2020
Fair Value Measurements  
Schedule of assets measured at fair value on a recurring basis

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Fair Value Measurements as of March 31, 2020

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Total

    

Level 1

    

Level 2

    

Level 3

Cash and cash equivalents

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$

289,544

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$

289,544

​

$

—

​

$

—

Marketable securities

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​

​

​

​

​

​

​

​

​

​

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Bonds and bond funds

​

$

179,964

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$

—

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$

179,964

​

$

—

Commercial paper

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108,387

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—

​

 

108,387

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—

​

​

​

288,351

​

 

—

​

 

288,351

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—

Total assets measured at fair value

​

$

577,895

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$

289,544

​

$

288,351

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$

—

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Fair Value Measurements as of December 31, 2019

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Total

    

Level 1

    

Level 2

    

Level 3

Cash and cash equivalents

​

$

87,206

​

$

87,206

​

$

—

​

$

—

Marketable securities

​

​

​

​

​

​

​

​

​

​

​

​

Bonds and bond funds

​

$

267,243

​

$

—

​

$

267,243

​

$

—

Commercial paper

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165,723

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—

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165,723

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—

​

​

​

432,966

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—

​

 

432,966

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—

Total assets measured at fair value

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$

520,172

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$

87,206

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$

432,966

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$

—

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