Balance Sheet Components
 9 Months Ended
Sep. 30, 2016
Balance Sheet Related Disclosures [Abstract]  
Balance Sheet Components
Balance Sheet Components
Investments in Marketable Securities
The following table summarizes the Company's available for sale investments as of September 30, 2016 (in thousands):
 
 
Maturity (in years)
 
Amortized Cost
 
Unrealized Gains
 
Unrealized Losses
 
Estimated Fair Value
Short-term investments:
 
 
 
 
 
 
 
 
 
 
   Commercial paper
 
1 or less
 
$
1,493

 
$
—

 
$
—

 
$
1,493

   Corporate debt securities
 
1 or less
 
1,757

 
—

 
(1
)
 
1,756

Total short-term investments
 
 
 
$
3,250

 
$
—

 
$
(1
)
 
$
3,249

The following table summarizes the Company's available for sale investments as of December 31, 2015 (in thousands):
 
 
Maturity (in years)
 
Amortized Cost
 
Unrealized Gains
 
Unrealized Losses
 
Estimated Fair Value
Short-term investments:
 
 
 
 
 
 
 
 
 
 
   Corporate debt securities
 
1 or less
 
$
7,420

 
$
—

 
$
(5
)
 
$
7,415

Total short-term investments
 
 
 
$
7,420

 
$
—

 
$
(5
)
 
$
7,415


At each reporting date, the Company reviews its investments for impairment to determine if unrealized losses are other-than-temporary. For debt securities, management determines whether it intends to sell the impaired securities, and if there is no intent or expected requirement to sell, management considers whether it is likely that the amortized cost will be recovered. The Company does not consider unrealized losses on its debt investment securities to be credit-related. These unrealized losses relate to changes in interest rates and market spreads subsequent to purchase. The Company has not made a decision to sell securities with unrealized losses and believes it is more likely than not that it would not be required to sell such securities before recovery of its amortized cost. There have been no other-than-temporary losses recognized in earnings in any of the periods presented.
Accrued Liabilities
Accrued liabilities consisted of the following (in thousands):
 
September 30,
 
December 31,
 
2016
 
2015
Clinical trials
$
2,152

 
$
1,666

Compensation and related expenses
832

 
993

Professional services
194

 
319

Interest expense and other
77

 
155

Total accrued liabilities
$
3,255

 
$
3,133