XML 71 R61.htm IDEA: XBRL DOCUMENT v3.10.0.1
Investments - Additional Information (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]      
Short term investments average maturity period 1 year 2 months 18 days 1 year 6 months 29 days  
Purchase of investments in equity - long term $ 6,163 $ 0 $ 0
Increase in fair value of investments in equity 800    
Carrying value of long-term investments in equity 6,963 $ 0  
Commitment to acquire future long-term investments $ 21,300