CONDENSED BALANCE SHEETS (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2015	Dec. 31, 2014
Stockholders' equity
Preferred Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred Stock, shares authorized (in shares)	5,000,000	5,000,000
Series A Junior Participating Preferred Stock, shares authorized (in shares)	25,000	25,000
Preferred Stock, shares issued (in shares)	0	0
Preferred Stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	250,000,000	250,000,000
Common stock, shares issued (in shares)	55,927,197	55,921,986
Common stock, shares outstanding (in shares)	55,927,197	55,921,986
Treasury stock (in shares)	199,275	199,275