Balance Sheets (unaudited) (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	1,000	1,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0017	$ 0.0017
Common stock, shares authorized	320,000	320,000
Common stock, shares issued	160,443	160,396
Common stock, shares outstanding	157,751	157,704
Treasury stock, shares	2,692	2,692