Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accounts receivable allowance	$ 1,923	$ 1,985
Driver's advances and other receivables, allowance	$ 634	$ 626
Common Class A [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, shares issued (in shares)	16,075,810	16,015,708
Common stock, shares outstanding (in shares)	16,075,810	16,015,708
Common Class B [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	5,000,000	5,000,000
Common stock, shares issued (in shares)	2,350,000	2,350,000
Common stock, shares outstanding (in shares)	2,350,000	2,350,000