Note 10 - Reconciliation of Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income tax benefit using U.S. federal statutory rate	$ (7,315)	$ (1,136)	$ (2,690)
Permanent differences	260	124	$ 299
Orphan Drug credit permanent addback	1,310	674
State income taxes, net of federal benefit	(808)	(303)	$ (389)
Tax credits	$ (4,219)	(2,176)	(7,164)
Expired net operating losses and tax credits		312	2,566
Change in valuation allowance	$ 9,782	4,394	$ 7,286
Mark-to-market derivative liability		(1,779)
Other	$ 990	$ (110)	$ 92