Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Accounts receivable allowance	$ 3,361	$ 2,992
Driver's advances and other receivables, allowance	$ 558	$ 764
Treasury stock, shares (in shares)	1,798,426	1,398,925
Common Class A [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	40,000,000	40,000,000
Common stock, shares issued (in shares)	16,211,918	16,183,139
Common stock, shares outstanding (in shares)	14,413,492	14,784,214
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