CONDENSED BALANCE SHEETS (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2016	Dec. 31, 2015
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
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)	68,371,643	66,480,065
Common stock, shares outstanding (in shares)	68,371,643	66,480,065
Series A Junior Participating Preferred Stock [Member]
Stockholders' equity:
Preferred Stock, shares authorized (in shares)	25,000	25,000