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Short-term Investments - Narrative (Details)
$ in Thousands
12 Months Ended
Dec. 31, 2019
USD ($)
investment
Dec. 31, 2018
USD ($)
Investments, Debt and Equity Securities [Abstract]    
Debt securities, available-for-sale, realized gain $ 594 $ 20
Debt securities, available-for-sale, realized gain $ 118 $ 1,300
Number of securities in a gross unrealized loss position | investment 4  
Number of securities in a gross unrealized loss position for more than twelve months | investment 2  
Unrealized loss $ 11