Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 15	$ 115
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	27,303,000	26,730,000
Common stock, shares outstanding	23,733,000	23,236,000
Treasury stock, shares	3,570,000	3,494,000