XML 54 R40.htm IDEA: XBRL DOCUMENT v3.21.2
Fair Value of Financial Instruments - Marketable securities portfolio (Details) - Debt securities (government) - USD ($)
$ in Thousands
9 Months Ended
Sep. 30, 2021
Dec. 31, 2020
Summary of marketable security portfolio    
Amortized Cost $ 285,135 $ 288,199
Net Unrealized Gains   170
Net Unrealized Losses (81)  
Estimated Fair Value $ 285,054 $ 288,369
Minimum    
Summary of marketable security portfolio    
Contractual maturity dates 12 months  
Maximum    
Summary of marketable security portfolio    
Contractual maturity dates 18 months