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Financial Instruments - Summary of Marketable Securities (Details) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Marketable Securities [Line Items]    
Debt securities, Cost $ 118,263 $ 45,782
Debt securities, Gross Unrealized Gains 29 33
Debt securities, Gross Unrealized Losses (46) (13)
Debt securities, Allowance for Credit Losses 0  
Debt securities, Estimated Fair Values 118,246 45,802
Equity securities, Cost 3,849 6,006
Equity securities, Gross Unrealized Gains 0 0
Equity securities, Gross Unrealized Losses 0 (2,281)
Equity securities, Allowance for Credit Losses 0  
Equity securities, Estimated Fair Values 3,849 3,725
Marketable securities, Cost 122,112 51,788
Marketable securities, Gross Unrealized Gains 29 33
Marketable securities, Gross Unrealized Losses (46) (2,294)
Marketable securities, Allowance for Credit Losses 0  
Marketable securities, Estimated Fair Values 122,095 49,527
Available-for-sale debt securities    
Marketable Securities [Line Items]    
Marketable securities, Estimated Fair Values 86,947 45,802
Corporate bonds and notes    
Marketable Securities [Line Items]    
Debt securities, Cost 69,973 41,730
Debt securities, Gross Unrealized Gains 29 29
Debt securities, Gross Unrealized Losses (42) (13)
Debt securities, Allowance for Credit Losses 0  
Debt securities, Estimated Fair Values 69,960 41,746
Commercial paper    
Marketable Securities [Line Items]    
Debt securities, Cost 15,991 4,052
Debt securities, Gross Unrealized Gains 0 4
Debt securities, Gross Unrealized Losses (4) 0
Debt securities, Allowance for Credit Losses 0  
Debt securities, Estimated Fair Values 15,987 4,056
Treasury and agency notes and bills    
Marketable Securities [Line Items]    
Debt securities, Cost 32,299  
Debt securities, Gross Unrealized Gains 0  
Debt securities, Gross Unrealized Losses 0  
Debt securities, Allowance for Credit Losses 0  
Debt securities, Estimated Fair Values 32,299  
Money market funds    
Marketable Securities [Line Items]    
Equity securities, Cost 3,849 2,601
Equity securities, Gross Unrealized Gains 0 0
Equity securities, Gross Unrealized Losses 0 0
Equity securities, Allowance for Credit Losses 0  
Equity securities, Estimated Fair Values 3,849 2,601
Cash and cash equivalents    
Marketable Securities [Line Items]    
Marketable securities, Estimated Fair Values 35,148  
Marketable equity securities    
Marketable Securities [Line Items]    
Equity securities, Cost   3,405
Equity securities, Gross Unrealized Gains   0
Equity securities, Gross Unrealized Losses   (2,281)
Equity securities, Estimated Fair Values $ 0 1,124
Equity securities    
Marketable Securities [Line Items]    
Marketable securities, Estimated Fair Values   $ 1,124