Quarterly report pursuant to Section 13 or 15(d)

Cash, Cash Equivalents and Investments (Details)

v3.7.0.1
Cash, Cash Equivalents and Investments (Details) - USD ($)
$ in Thousands
Jun. 30, 2017
Dec. 31, 2016
Jun. 30, 2016
Dec. 31, 2015
Cash and cash equivalents [Abstract]        
Cost or Amortized Cost $ 110,343 $ 106,932 $ 116,273 $ 65,126
Total Cash and Cash Equivalents [Member]        
Cash and cash equivalents [Abstract]        
Cost or Amortized Cost 110,336 106,932    
Gross Unrealized Gains 9 0    
Gross Unrealized Losses (2) 0    
Estimated Fair Value 110,343 106,932    
Total Short-Term Investments [Member]        
Cash and cash equivalents [Abstract]        
Cost or Amortized Cost 0 1,500    
Gross Unrealized Gains 0 13    
Gross Unrealized Losses 0 (2)    
Estimated Fair Value 0 1,511    
Cash and Cash Equivalents and Short-term Investments [Member]        
Cash and cash equivalents [Abstract]        
Cost or Amortized Cost 110,336 108,432    
Gross Unrealized Gains 9 13    
Gross Unrealized Losses (2) (2)    
Estimated Fair Value 110,343 108,443    
Cash [Member] | Total Cash and Cash Equivalents [Member]        
Cash and cash equivalents [Abstract]        
Cost or Amortized Cost 103,859 101,987    
Gross Unrealized Gains 0 0    
Gross Unrealized Losses 0 0    
Estimated Fair Value 103,859 101,987    
Money Market [Member] | Total Cash and Cash Equivalents [Member]        
Cash and cash equivalents [Abstract]        
Cost or Amortized Cost 6,477 4,945    
Gross Unrealized Gains 9 0    
Gross Unrealized Losses (2) 0    
Estimated Fair Value 6,484 4,945    
Corporate Bonds and Asset Backed Securities [Member] | Total Short-Term Investments [Member]        
Cash and cash equivalents [Abstract]        
Cost or Amortized Cost 0 1,500    
Gross Unrealized Gains 0 13    
Gross Unrealized Losses 0 (2)    
Estimated Fair Value $ 0 $ 1,511