CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
CONDENSED CONSOLIDATED BALANCE SHEETS
Accounts receivable allowance for doubtful accounts	$ 1,501	$ 1,568
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	170,000,000	170,000,000
Common stock, shares issued	19,527,867	19,360,026
Common stock, shares outstanding	18,091,066	17,946,386
Treasury stock at par	1,436,801	1,413,640