Note 13 - Income Taxes - Reconciliation of Income Taxes Computed (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2016
U.S. Federal statutory rate	21.00%	34.00%	34.00%
State income taxes, net of Federal benefit	0.90%	1.50%	10.80%
Foreign rate differential	0.00%	(0.60%)	2.60%
Research and experimental and Orphan Drug tax credit	2.30%	6.40%	(50.60%)
Effect of federal and state tax rate changes	0.30%	(6.10%)	(43.00%)
Tax Reform Impact	0.00%	13.90%	0.00%
Change in fair value of contingent consideration liability	1.80%	(1.40%)	(12.40%)
Stock option shortfalls	(2.20%)	(3.10%)	22.30%
Other	(0.50%)	(0.10%)	0.10%
Change in valuation allowance	(21.20%)	(25.90%)	50.90%
Effective tax rate	2.40%	18.60%	14.70%	14.70%