BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 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)	66,480,065	55,921,986
Common stock, shares outstanding (in shares)	66,480,065	55,921,986
Treasury stock (in shares)	0	199,275