Balance Sheet Parentheticals - USD ($) shares in Thousands, $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Allowance for doubtful accounts receivable	$ 4	$ 4
Accumulated depreciation and amortization, property and equipment	$ 58,623	$ 59,875
Preferred stock, par value per share	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000	5,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value per share	$ 0.001	$ 0.001
Common stock, shares authorized	225,000	225,000
Treasury stock, shares	122	306
Common Stock
Common stock, shares issued	105,711	104,582