Balance Sheet Parenthetical (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Restricted investments	430	430
Allowances for accounts receivable	35	35
Accumulated depreciation and amortization, property and equipment	82,576	80,535
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	380	218
Common Stock [Member]
Common stock, shares issued	481,168	480,389