Note 3 - Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2020

Notes Tables

Fair Value, Assets Measured on Recurring Basis [Table Text Block]

			Fair Value Measurements Using
	Balance at		Quoted Prices in		Significant		Significant
	March 31,		Active Markets		Other		Unobservable
(in thousands)	2020		for Identical		Observable		Inputs
			Items		Inputs		(Level 3)
			(Level 1)		(Level 2)
Assets
Restricted cash held as a certificate of deposit	$	324	$	324	$	—	$	—
Deposit held as a certificate of deposit		151		151		—		—
Total assets	$	475	$	475	$	—	$	—
Liabilities
Warrant liability	$	3,952	$	—	$	—	$	3,952
Embedded derivative liability		1		—		—		1
Total liabilities	$	3,953	$	—	$	—	$	3,953

			Fair Value Measurements Using
	Balance at		Quoted Prices in		Significant		Significant
	December 31,		Active Markets		Other		Unobservable
(in thousands)	2019		for Identical		Observable		Inputs
			Items		Inputs		(Level 3)
			(Level 1)		(Level 2)
Assets
Restricted cash held as a certificate of deposit	$	324	$	324	$	—	$	—
Deposit held as a certificate of deposit		151		151		—		—
Total assets	$	475	$	475	$	—	$	—
Liabilities
Warrant liability	$	4,089	$	—	$	—	$	4,089
Embedded derivative liability		3		—		—		3
Total liabilities	$	4,092	$	—	$	—	$	4,092

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]

(in thousands)	Level 3
	liabilities
Fair value of warrant liability and embedded derivative liability at December 31, 2019	$	4,092
Decrease in fair value of warrant liability at March 31, 2020		(122	)
Decrease in fair value of embedded derivative liability at March 31, 2020		(2	)
Decrease in fair value related to warrants expired		(15	)
Fair value of warrant liability and embedded derivative liability at March 31, 2020	$	3,953