Balance Sheet Parenthetical (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Allowances for accounts receivable	$ 4	$ 4
Accumulated depreciation and amortization, property and equipment	59,459	58,623
Accumulated intangible assets amortization	$ 2,354	$ 1,471
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	236	122
Common Stock
Common stock, shares issued	106,115	105,711