Condensed Consolidated Balance Sheets (Unaudited) (Parentheticals) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounts receivable allowance	$ 1,817	$ 1,460
Drivers' advances and other receivables, allowance	$ 672	$ 496
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)	15,996,066	15,979,703
Common stock, shares outstanding (in shares)	15,996,066	15,979,703
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