Note 8 - Stock Based Awards (Tables)

6 Months Ended

Jun. 30, 2021

Notes Tables

Share-based Payment Arrangement, Option, Activity [Table Text Block]

						Weighted
						Average
				Weighted		Remaining		Aggregate
				Average		Contractual		Intrinsic
	Number of			Exercise		Life		Value
	Shares			Price		(in years)		(in thousands)
Balances, January 1, 2021		2,173,776		$	9.59
Options granted		608,950			6.02
Options cancelled		(343,537	)		43.89
Options exercised		(140,952	)		1.98
Balances, June 30, 2021		2,298,237		$	3.99		7.1	$	5,905
Outstanding and expected to vest as of June 30, 2021		2,125,891		$	3.77		6.9	$	5,871
Exercisable as of June 30, 2021		1,373,881		$	2.12		5.6	$	5,707

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	June 30,			June 30,
	2021			2020
Expected volatility		113.4	%		78.1	%
Risk-free interest rate		0.7	%		0.8	%
Dividend yield		0.0	%		0.0	%
Expected life (in years)		6.1			3.9