Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts	$ 23,367	$ 24,418
Preferred stock par value	$ 0.0001	$ 0.0001
Preferred stock authorized	7,500,000	7,500,000
Preferred stock issued	0	0
Preferred stock outstanding	0	0
Common Class A [Member]
Common stock par value	$ 0.0001	$ 0.0001
Common stock authorized	80,000,000	80,000,000
Common stock issued	24,454,048	24,230,448
Common stock outstanding	24,453,926	24,230,326
Common Class B [Member]
Common stock par value	$ 0.0001	$ 0.0001
Common stock authorized	20,000,000	20,000,000
Common stock issued	5,123,883	5,130,558
Common stock outstanding	5,122,966	5,129,641
Treasury Class-A [Member]
Treasury Stock, Shares	122	122
Treasury Class B [Member]
Treasury Stock, Shares	917	917