XML 61 R51.htm IDEA: XBRL DOCUMENT v3.20.2
Investments - Additional Information (Details)
3 Months Ended 9 Months Ended
Sep. 30, 2020
USD ($)
Sep. 30, 2019
USD ($)
Sep. 30, 2020
USD ($)
Sep. 30, 2019
USD ($)
Dec. 31, 2019
USD ($)
Investment
Schedule Of Available For Sale Securities [Line Items]          
Available-for-sale investments $ 0   $ 0   $ 73,065,000
Realized gains or losses $ 0 $ 0   $ 0  
Maximum          
Schedule Of Available For Sale Securities [Line Items]          
Realized gains or losses     $ 100,000    
US Treasury Bonds          
Schedule Of Available For Sale Securities [Line Items]          
Available-for-sale investments         $ 73,065,000
Number of investments in unrealized loss position for less than 12 months | Investment         4
Investments in unrealized loss position for less than 12 months, fair value         $ 18,000,000