Note 2 - Fair Value Measurement - Financial Assets on Recurring Basis (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Inputs, Level 2 [Member]
Total cash and cash equivalents	$ 0	$ 0
Fair Value, Measurements, Recurring [Member]
Total cash and cash equivalents	32,380,674	6,663,318
Fair Value, Measurements, Recurring [Member] | Bank Time Deposits [Member]
Cash and cash equivalents	32,327,287	6,610,183
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Cash and cash equivalents	53,387	53,135
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Total cash and cash equivalents	32,380,674	6,663,318
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Bank Time Deposits [Member]
Cash and cash equivalents	32,327,287	6,610,183
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Cash and cash equivalents	53,387	53,135
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Total cash and cash equivalents
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Bank Time Deposits [Member]
Cash and cash equivalents
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
Cash and cash equivalents