Quarterly report pursuant to Section 13 or 15(d)

Cash, Cash Equivalents and Investments - Narrative (Details)

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Cash, Cash Equivalents and Investments - Narrative (Details)
3 Months Ended 6 Months Ended
Jun. 30, 2016
USD ($)
security
Jun. 30, 2016
USD ($)
security
Jun. 30, 2015
USD ($)
Cash and Cash Equivalents [Abstract]      
Number of owned securities that were in an unrealized loss position | security 25 25  
Unrealized losses deemed to be other-than-temporary, recognized $ 0 $ 0  
Proceeds from sale of investments $ 500,000 $ 500,000 $ 3,662,000