BALANCE SHEETS (Parenthetical) (USD $)	Jun. 30, 2011	Dec. 31, 2010
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	2,000,000	2,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	115,125,113	111,492,014
Common stock, shares outstanding	114,669,683	111,036,584
Treasury stock, shares	455,430	455,430