Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 14,235	$ 10,326
Common stock, shares authorized	20,000,000	20,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares issued	6,687,000	6,592,000
Common stock, shares outstanding	6,455,000	6,361,000
Treasury stock, shares	232,000	232,000