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Short-term and Long-term Investments (Tables)
6 Months Ended
Jun. 30, 2017
Investments, Debt and Equity Securities [Abstract]  
Summary of Amortized Cost, Gross Unrealized Gains and Losses, and Fair Value of Short-term and Long-term Investments
The following table summarizes the amortized cost, gross unrealized gains and losses, and fair value of available-for-sale investments as of June 30, 2017:
 
Amortized
Cost
 
Gross
Unrealized
Gains
 
Gross
Unrealized
Losses
 
Aggregate
Fair Value
U.S. government debt securities
$
92,081

 
$

 
$
(94
)
 
$
91,987

Corporate notes and bonds
542

 

 

 
542

Certificates of deposit
275

 

 

 
275

Total
$
92,898

 
$

 
$
(94
)
 
$
92,804

The following table summarizes the amortized cost, gross unrealized gains and losses, and fair value of available-for-sale investments as of December 31, 2016:
 
Amortized
Cost
 
Gross
Unrealized
Gains
 
Gross
Unrealized
Losses
 
Aggregate
Fair Value
U.S. government debt securities
$
180,412

 
$
5

 
$
(94
)
 
$
180,323

Certificates of deposit
272

 

 

 
272

Total
$
180,684

 
$
5

 
$
(94
)
 
$
180,595