Quarterly Financial Data (unaudited) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Data [Abstract]
Total revenues	$ 100,000	$ 0	$ 200,000	$ 0	$ 100,000	$ 0	$ 0	$ 0
Net income (loss)	(27,218,000)	(9,980,000)	(3,423,000)	(6,864,000)	3,849,000	1,584,000	(13,262,000)	(10,135,000)	(47,485,437)	(17,963,873)	(14,424,545)
Net income (loss) applicable to common stockholders	$ (27,218,000)	$ (9,980,000)	$ (3,423,000)	$ (6,864,000)	$ 3,849,000	$ 1,584,000	$ (13,262,000)	$ (10,135,000)
Basic and diluted income (loss) per share applicable to common stock (in dollars per share)	$ (0.68)	$ (0.33)	$ (0.11)	$ (0.23)	$ 0.14	$ 0.07	$ (0.63)	$ (0.49)	$ (1.44)	$ (0.78)	$ (0.80)