Note 2 - Revenue Recognition (Details Textual) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenue from Contract with Customer, Excluding Assessed Tax	$ 10,394,000	$ 10,671,000	$ 20,126,000	$ 20,643,000
Contract with Customer, Asset, Credit Loss Expense (Reversal)	0	0	0	0
Capitalized Contract Cost, Amortization	4,000	31,000	9,000	53,000
Capitalized Contract Cost, Impairment Loss	0	0	0	0
Transferred at Point in Time [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	9,900,000	10,200,000	19,100,000	19,000,000.0
Transferred over Time [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 500,000	$ 500,000	$ 1,000,000.0	$ 1,700,000