Quarterly report pursuant to Section 13 or 15(d)

Note 6 - Fair Value Measurements and Financial Instruments - Assets Measured on a Recurring Basis (Details)

v3.19.3
Note 6 - Fair Value Measurements and Financial Instruments - Assets Measured on a Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($)
$ in Thousands
Sep. 30, 2019
Dec. 31, 2018
Assets, fair value $ 29,891 $ 15,118
Fair Value, Inputs, Level 1 [Member]    
Assets, fair value
Fair Value, Inputs, Level 2 [Member]    
Assets, fair value 29,891 15,118
Fair Value, Inputs, Level 3 [Member]    
Assets, fair value
Bank Time Deposits [Member]    
Assets, fair value 1,889 496
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 1,889 496
Bank Time Deposits [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value
Corporate Debt Securities [Member]    
Assets, fair value 9,977  
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]    
Assets, fair value  
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]    
Assets, fair value 9,977  
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value  
US Treasury Securities [Member]    
Assets, fair value   3,989
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   3,989
US Treasury Securities [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value  
Canadian Provincial Promissory Notes [Member]    
Assets, fair value 4,489 5,991
Canadian Provincial Promissory Notes [Member] | Fair Value, Inputs, Level 1 [Member]    
Assets, fair value
Canadian Provincial Promissory Notes [Member] | Fair Value, Inputs, Level 2 [Member]    
Assets, fair value 4,489 5,991
Canadian Provincial Promissory Notes [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value
Investments [Member]    
Assets, fair value 13,536 4,642
Investments [Member] | Fair Value, Inputs, Level 1 [Member]    
Assets, fair value
Investments [Member] | Fair Value, Inputs, Level 2 [Member]    
Assets, fair value 13,536 4,642
Investments [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value