Basis of Presentation (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Basis of Presentation
Cash, cash equivalents and marketable securities	$ 136,600,000		$ 136,600,000
Working capital	123,200,000		123,200,000
Net Loss	(23,140,000)	(15,027,000)	(59,488,000)	(42,316,000)
Net cash used in operations			$ (52,712,000)	$ (36,456,000)