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Investments (Tables)
 12 Months Ended
Dec. 31, 2017
Investments [Abstract]  
Summary of Short-term Investments

Investments as of December 31, 2017 consisted of the following:







 

 

 

 

 

 

 

 

 



 

 

 

 

 

 

 

 

 



 

 

 

 

Unrealized

 

 

 



 

 

 

 

Gains

 

 

 



 

Cost Basis

 

(Losses)

 

Fair Value

Corporate bonds

 

$

 2,925 

 

$

 (5)

 

$

 2,920 

U.S. government agencies and securities

 

 

 3,000 

 

 

 (1)

 

 

 2,999 

Commercial paper

 

 

 6,723 

 

 

 —

 

 

 6,723 

Total

 

$

 12,648 

 

$

 (6)

 

$

 12,642 



Investments as of December 31, 2016 consisted of the following:







 

 

 

 

 

 

 

 

 



 

 

 

 

 

 

 

 

 



 

 

 

 

Unrealized

 

 

 



 

 

 

 

Gains

 

 

 



 

Cost Basis

 

(Losses)

 

Fair Value

Corporate bonds

 

$

 8,284 

 

$

 (8)

 

$

 8,276 

U.S. government agencies and securities

 

 

 8,542 

 

 

 (13)

 

 

 8,529 

Commercial paper

 

 

 5,996 

 

 

 —

 

 

 5,996 

Total

 

$

 22,822 

 

$

 (21)

 

$

 22,801