Note 16 - Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]

	Year Ending December 31,
(in thousands)	2019			2018			2017
United States	$	(9,652	)	$	(6,541	)	$	(7,400	)
International		—			—			—
	$	(9,652	)	$	(6,541	)	$	(7,400	)

Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]

	Year Ending December
(in thousands)	2019		2018		2017
Current
Federal	$	—	$	—	$	—
State		6		4		3
Other		—		—		—
Total current tax expense		6		4		3
Deferred
Federal		—		—		—
State		—		—		—
Other		—		—		—
Total deferred tax expense		—		—		—
Income tax provision	$	6	$	4	$	3

Schedule of Deferred Tax Assets and Liabilities [Table Text Block]

	December 31
(in thousands)	2019			2018
Deferred tax assets:
Net operating losses	$	29,427		$	26,790
Accruals		222			446
Deferred revenue		—			10
Stock options		1,191			1,425
Other deferred tax assets		765			716
Property and equipment		6			9
Lease liability		301			—
Total deferred tax assets		31,912			29,396
Deferred tax liabilities:
Lease asset		(301	)		—
Total deferred tax liabilities		(301	)		—
Valuation allowance		(31,611	)		(29,396	)
Net deferred taxes	$	—		$	—

Summary of Operating Loss Carryforwards and Tax Credit Carryforwards [Table Text Block]

			Expiration
	Amount		Years
Net operating losses, federal (Post December 31, 2017)	$	16,151	Do Not Expire
Net operating losses, federal (Pre January 1, 2018)	$	94,886	Beginning in 2024
Net operating losses, state	$	90,455	Beginning in 2028
Tax credits, federal	$	1,316	Beginning in 2026
Tax credits, state	$	325	Indefinite

Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]

	Year ended December 31,
(in thousands)	2019		2018
Unrecognized benefit - beginning of period	$	974	$	931
Gross decreases - prior period tax positions		—		43
Unrecognized benefit - end of period	$	974	$	974

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

	Year Ending December 31,
	2019			2018			2017
Statutory Rate		21.0	%		21.0	%		34.0	%
State Tax		3.1	%		(0.3	%)		0.2	%
Stock Based Compensation Expense		(3.7	%)		(4.3	%)		(2.1	%)
Change in Valuation Allowance		(23.0	%)		(13.0	%)		141.7	%
Other		(0.3	%)		(0.5	%)		0.7	%
Warrant/equity expenses		1.7	%		4.2	%		(0.5	%)
Impact of 162m		1.1	%		1.3	%		(4.6	%)
Tax Reform - Tax Rate Change		0.0	%		0.0	%		(169.5	%)
Impact of ASC 606		0.0	%		(8.5	%)		0.0	%
Total		(0.1	%)		(0.1	%)		(0.1	%)