Balance Sheet Parentheticals - USD ($) shares in Thousands, $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Restricted investments	$ 0	$ 0
Allowance for doubtful accounts receivable	4	4
Accumulated depreciation and amortization, property and equipment	$ 59,875	$ 59,428
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	306	237
Common Stock
Common stock, shares issued	104,582	103,860