Condensed Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	Sep. 30, 2011	Dec. 31, 2010
Condensed Balance Sheets [Abstract]
Accounts receivable, allowance for losses	$ 916	$ 1,603
Preferred stock, par value	$ 10	$ 10
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	48,147,969	48,147,969
Treasury stock, shares	18,407,024	15,854,205