Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.2
Note 6 - Fair Value Measurements and Financial Instruments - Assets Measured on a Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($)
$ in Thousands
Jun. 30, 2019
Dec. 31, 2018
Assets, fair value $ 35,048 $ 15,118
Fair Value, Inputs, Level 1 [Member]    
Assets, fair value
Fair Value, Inputs, Level 2 [Member]    
Assets, fair value 35,048 15,118
Fair Value, Inputs, Level 3 [Member]    
Assets, fair value
Bank Time Deposits [Member]    
Assets, fair value 3,917 496
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 3,917 496
Bank Time Deposits [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value
US Treasury Securities [Member]    
Assets, fair value 5,480 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 5,480 3,989
US Treasury Securities [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value
Corporate Debt Securities [Member]    
Assets, fair value 4,978  
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 4,978  
Corporate Debt 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
Debt Security, Government, Non-US [Member]    
Assets, fair value 2,492  
Debt Security, Government, Non-US [Member] | Fair Value, Inputs, Level 1 [Member]    
Assets, fair value  
Debt Security, Government, Non-US [Member] | Fair Value, Inputs, Level 2 [Member]    
Assets, fair value 2,492  
Debt Security, Government, Non-US [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value  
Investments [Member]    
Assets, fair value 13,692 4,642
Investments [Member] | Fair Value, Inputs, Level 1 [Member]    
Assets, fair value
Investments [Member] | Fair Value, Inputs, Level 2 [Member]    
Assets, fair value 13,692 4,642
Investments [Member] | Fair Value, Inputs, Level 3 [Member]    
Assets, fair value