Balance Sheet Parenthetical (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Restricted investments	$ 430	$ 430
Allowances for accounts receivable	35	35
Accumulated depreciation and amortization, property and equipment	$ 81,533	$ 83,416
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	900,000	900,000
Treasury stock, shares	814	380
Common Stock [Member]
Common stock, shares issued	514,275	512,375