Basis of Presentation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Basis of Presentation
Cash, cash equivalents and marketable securities	$ 203,200		$ 203,200
Net Loss	$ (29,598)	$ (31,980)	(96,223)	$ (94,513)
Net cash used in operations			$ (92,687)	$ (85,142)