Note 10 - Stock Options and Restricted Stock (Details Textual) - USD ($)				3 Months Ended
	Jan. 04, 2021	Jan. 01, 2016	Jul. 27, 2010	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Jul. 18, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance (in shares)				4,902			11,569
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)				0	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period (in shares)				0	0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value				$ 0
Share-based Payment Arrangement, Nonemployee [Member]
Stock Issued During Period, Value, Issued for Services	$ 311,000
Deferred Compensation Share-based Arrangements, Liability, Current and Noncurrent						$ 221,000
Stock Issued During Period, Shares, Issued for Services (in shares)				118,184
Share-based Payment Arrangement, Option [Member]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total				$ 0
Share-based Payment Arrangement, Option [Member] | Selling, General and Administrative Expenses [Member]
Share-based Payment Arrangement, Expense				$ 0	$ 2,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)				165,000
Restricted Stock [Member] | Share-based Payment Arrangement, Nonemployee [Member]
Share-based Payment Arrangement, Expense				$ 23,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)				48,129
Restricted Stock [Member] | Selling, General and Administrative Expenses [Member]
Share-based Payment Arrangement, Expense				$ 24,000	$ 36,000
Option Plan 2010 Member
Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Outstanding Stock Maximum			15.00%
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)		381,272		0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance (in shares)		2,541,809		1,079
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)		5 years
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)								159,448
Option Plan 2010 Member | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)		1 year
Option Plan 2010 Member | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)		3 years
The 2016 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)				3,823				692,782
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance (in shares)				184,503
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)								533,334