Note 2 - Revenue Recognition (Details Textual) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020
Revenue from Contract with Customer, Excluding Assessed Tax, Total	$ 9,078,000	$ 10,646,000	$ 10,671,000	$ 9,972,000	$ 11,071,000	$ 10,420,000	$ 8,924,000	$ 16,729,000	$ 40,367,000	$ 47,144,000
Contract with Customer, Asset, Credit Loss Expense (Reversal)									0	0
Capitalized Contract Cost, Impairment Loss										0
Capitalized Contract Cost, Amortization									61,000	89,000
Transferred at Point in Time [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total									38,100,000	43,700,000
Transferred over Time [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Total									$ 2,300,000	$ 3,400,000