Description of Business and Development Stage Activities (Details) (USD $)	12 Months Ended			163 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012	Nov. 10, 2011	Nov. 16, 2011 Initial Public Offering	Feb. 04, 2013 Follow-on Offering
Development Stage Enterprises [Abstract]
Net Income (Loss) Attributable to Parent	$ (23,321,000)	$ (18,087,000)	$ (16,213,000)	$ (104,757,000)
Deficit accumulated during the development stage	(104,797,000)	(81,476,000)		(104,797,000)
Financings
FInancing proceeds						37,600,000	49,000,000
Financing price per share						$ 7.00	$ 11.40
Financing shares						6,200,000	4,600,000
Financing underwriting discounts and commissions						3,000,000
Financing offering expenses						2,900,000
Pre-IPO convertible preferred stock					14,270,113
Post-IPO converted common stock					10,719,353
Financing received	$ 1,300,000	$ 42,600,000