Note 3 - Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2021

Notes Tables

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

			Fair Value Measurements Using
	Balance at March 31, 2021		Quoted Prices in Active Markets for Identical Items (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets
Restricted cash held as a certificate of deposit	$	324	$	324	$	—	$	—
Deposit held as a certificate of deposit		151		151		—		—
Total assets	$	475	$	475	$	—	$	—

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