XML 34 R51.htm IDEA: XBRL DOCUMENT v3.19.3.a.u2
Cash, Cash Equivalents, Marketable Securities, and Restricted Cash - Cash and Available for Sale Securities (Details) - USD ($)
$ in Thousands
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]      
Cash and cash equivalents $ 142,837 $ 79,749 $ 49,060
Cost, debt securities 309,665 424,830  
Cost, cash balances and debt securities 452,502 504,579  
Gross Unrealized Gain 255 11  
Gross Unrealized Loss (17) (438)  
Fair value, cash balances 142,837 79,749  
Debt securities, available-for-sale 309,903 424,403  
Fair value, cash balances and debt securities 452,740 504,152  
Marketable securities with maturity date greater than 12 months 9,500    
Corporate debt securities      
Debt Securities, Available-for-sale [Line Items]      
Cost, debt securities 145,875 240,969  
Gross Unrealized Gain 121 7  
Gross Unrealized Loss (5) (250)  
Debt securities, available-for-sale 145,991 240,726  
Commercial paper      
Debt Securities, Available-for-sale [Line Items]      
Cost, debt securities 73,659 115,245  
Gross Unrealized Gain 53 0  
Gross Unrealized Loss (2) (104)  
Debt securities, available-for-sale 73,710 115,141  
Asset-backed securities      
Debt Securities, Available-for-sale [Line Items]      
Cost, debt securities 77,731 68,215  
Gross Unrealized Gain 79 4  
Gross Unrealized Loss 0 (84)  
Debt securities, available-for-sale 77,810 68,135  
U.S. government agency bonds      
Debt Securities, Available-for-sale [Line Items]      
Cost, debt securities 11,999    
Gross Unrealized Gain 2    
Gross Unrealized Loss (10)    
Debt securities, available-for-sale 11,991    
Money market      
Debt Securities, Available-for-sale [Line Items]      
Cost, debt securities 350 350  
Gross Unrealized Gain 0 0  
Gross Unrealized Loss 0 0  
Debt securities, available-for-sale 350 350  
Certificates of deposit      
Debt Securities, Available-for-sale [Line Items]      
Cost, debt securities 51 51  
Gross Unrealized Gain 0 0  
Gross Unrealized Loss 0 0  
Debt securities, available-for-sale $ 51 $ 51