Note 6 - Valuation Accounts - Valuation and Allowance Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Parts Inventory [Member]
Balance	$ 9,315	$ 7,661	$ 7,050
Net Charged to Costs and Expenses	3,520	4,501	4,460
Net Write-Offs	(5,375)	(2,847)	(3,849)
Balance End of Year	7,460	9,315	7,661
Commercial Vehicle Inventory [Member]
Balance	6,075	9,602	4,587
Net Charged to Costs and Expenses	(536)	9,598	12,489
Net Write-Offs	(4,620)	(13,125)	(7,474)
Balance End of Year	$ 919	6,075	9,602
SEC Schedule, 12-09, Allowance, Credit Loss [Member]
Balance		1,014	987
Net Charged to Costs and Expenses			2,065
Net Write-Offs			(2,038)
Balance End of Year			1,014
Allowance for Warranty Receivables From Manufacturers [Member]
Balance		$ 410	429
Net Charged to Costs and Expenses			1,661
Net Write-Offs			(1,680)
Balance End of Year			$ 410