Annual report pursuant to Section 13 and 15(d)

Note 8 - Fair Value Measurements and Financial Instruments - Assets Measured on a Recurring Basis (Details)

v3.21.1
Note 8 - Fair Value Measurements and Financial Instruments - Assets Measured on a Recurring Basis (Details) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Assets, fair value $ 122,064  
Fair Value, Inputs, Level 1 [Member]    
Assets, fair value  
Fair Value, Inputs, Level 2 [Member]    
Assets, fair value 122,064  
Fair Value, Inputs, Level 3 [Member]    
Assets, fair value  
Fair Value, Recurring [Member]    
Assets, fair value   $ 95,960
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]    
Assets, fair value  
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]    
Assets, fair value   95,960
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value  
Money Market Accounts [Member]    
Assets, fair value 668  
Money Market Accounts [Member] | Fair Value, Inputs, Level 1 [Member]    
Assets, fair value  
Money Market Accounts [Member] | Fair Value, Inputs, Level 2 [Member]    
Assets, fair value 668  
Money Market Accounts [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value  
Bank Time Deposits [Member]    
Assets, fair value 48,397  
Bank Time Deposits [Member] | Fair Value, Inputs, Level 1 [Member]    
Assets, fair value  
Bank Time Deposits [Member] | Fair Value, Inputs, Level 2 [Member]    
Assets, fair value 48,397  
Bank Time Deposits [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value  
Bank Time Deposits [Member] | Fair Value, Recurring [Member]    
Assets, fair value   2,989
Bank Time Deposits [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]    
Assets, fair value  
Bank Time Deposits [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]    
Assets, fair value   2,989
Bank Time Deposits [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value  
Money Market Funds [Member]    
Assets, fair value 44,000  
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]    
Assets, fair value  
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]    
Assets, fair value 44,000  
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value  
Corporate Debt Securities [Member] | Fair Value, Recurring [Member]    
Assets, fair value   6,235
Corporate Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]    
Assets, fair value  
Corporate Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]    
Assets, fair value   6,235
Corporate Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value  
Canadian Provincial Promissory Notes [Member] | Fair Value, Recurring [Member]    
Assets, fair value   5,493
Canadian Provincial Promissory Notes [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]    
Assets, fair value  
Canadian Provincial Promissory Notes [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]    
Assets, fair value   5,493
Canadian Provincial Promissory Notes [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value  
US Treasury Securities [Member]    
Assets, fair value 5,000  
US Treasury Securities [Member] | Fair Value, Inputs, Level 1 [Member]    
Assets, fair value  
US Treasury Securities [Member] | Fair Value, Inputs, Level 2 [Member]    
Assets, fair value 5,000  
US Treasury Securities [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value  
Investments [Member] | Fair Value, Recurring [Member]    
Assets, fair value   81,243
Investments [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]    
Assets, fair value  
Investments [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]    
Assets, fair value   81,243
Investments [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value  
Canadian Treasury Securities [Member]    
Assets, fair value 23,999  
Canadian Treasury Securities [Member] | Fair Value, Inputs, Level 1 [Member]    
Assets, fair value  
Canadian Treasury Securities [Member] | Fair Value, Inputs, Level 2 [Member]    
Assets, fair value 23,999  
Canadian Treasury Securities [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value