Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ (2,786)	$ (2,852)
Property and equipment, accumulated depreciation	(55,736)	(51,099)
Intangible assets, accumulated amortization	$ (23,757)	$ (20,656)
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	30,000,000	30,000,000
Common stock, shares issued	19,021,853	18,787,816
Common stock, shares outstanding	17,739,431	17,128,825
Treasury stock, shares outstanding	1,282,422	1,658,991