Note 4 - Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2021

Notes Tables

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

	March 31, 2021						December 31, 2020
	Quoted Prices in		Direct or				Quoted Prices in		Direct or
	Active Markets		Indirect				Active Markets		Indirect
	for Identical		Observable				for Identical		Observable
	Assets (Level 1)		Inputs (Level 2)		Total		Assets (Level 1)		Inputs (Level 2)		Total
Assets
Cash equivalents:
Money market funds	$	6,114	$	—	$	6,114	$	6,114	$	—	$	6,114
Corporate commercial paper		—		—		—		—		—		—
Corporate debt		—		—		—		—		—		—
Total cash equivalents		6,114		—		6,114		6,114		—		6,114
Restricted cash:
Money market funds		337		—		337		337		—		337
Total assets measured at fair value	$	6,451	$	—	$	6,451	$	6,451	$	—	$	6,451