Note 13 - Income Taxes - Reconciliation of Income Taxes Computed (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
U.S. Federal statutory rate	21.00%	21.00%	34.00%
State income taxes, net of Federal benefit	0.30%	0.90%	1.50%
Foreign rate differential	0.00%	0.00%	(0.60%)
Research and experimental and Orphan Drug tax credit	3.40%	2.30%	6.40%
Effect of federal and state tax rate changes	(0.40%)	0.30%	(6.10%)
Tax Reform Impact	0.00%	0.00%	13.90%
Change in fair value of contingent consideration liability	(0.30%)	1.80%	(1.40%)
Stock option shortfalls	(0.90%)	(2.20%)	(3.10%)
NOL expiration	(1.20%)	0.00%	0.00%
Other	(1.40%)	(0.50%)	(0.10%)
Change in valuation allowance	(20.50%)	(21.20%)	(25.90%)
Effective tax rate	(0.03%)	2.40%	18.60%