FAIR VALUE MEASUREMENTS (Tables)
 3 Months Ended
Mar. 31, 2015
Fair Value Disclosures [Abstract]  
Financial assets and liabilities measured at fair value on a recurring basis
As of March 31, 2015 and December 31, 2014, the assets and liabilities measured at fair value consisted of the following (in thousands):

 
March 31, 2015
 
December 31, 2014
 
Fair Value Measurements Using Input Types
 
 
 
Fair Value Measurements Using Input Types
 
 
 
Level 2
 
Level 3
 
Total
 
Level 2
 
Level 3
 
Total
Assets:
 
 
 
 
 
 
 
 
 
 
 
Derivative assets
$
3,063

 
$
—

 
$
3,063

 
$
1,258

 
$
—

 
$
1,258

Non-marketable securities
—

 
3,667

 
3,667

 
—

 
3,384

 
3,384

     Total assets
$
3,063

 
$
3,667

 
$
6,730

 
$
1,258

 
$
3,384

 
$
4,642

Liabilities:
 
 
 
 
 
 
 
 
 
 
 
Derivatives liabilities
$
12

 
$
—

 
$
12

 
$
—

 
$
—

 
$
—
Fair value of non-marketable securities
The following table summarizes the change in the fair value of the Company's non-marketable securities during the three months ended March 31, 2015 (in thousands).

Balance as of December 31, 2014
$
3,384

Sales
—

Realized gains
59

Unrealized gains
224

Balance as of March 31, 2015
$
3,667