Note 7 - Leases - Summary of Rental Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Lease and rental expense	$ 24,393	$ 16,902	$ 12,764
Revenue Equipment [Member]
Lease and rental expense	20,989	14,682	12,055
Land and Building [Member]
Lease and rental expense	2,898	1,339	448
Other Machinery and Equipment [Member]
Lease and rental expense	$ 506	$ 881	$ 261