Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Allowance for doubtful accounts	$ 0	$ 0
Stockholders' Equity:
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	28,860,961	28,405,850
Common stock, shares outstanding	28,149,737	27,694,626
Treasury stock, shares	(711,231)	(711,231)