Nature of Business (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash and cash equivalents	$ 73,488	$ 73,662	$ 73,849	$ 30,198
Accumulated deficit	$ (203,689)	$ (148,885)
Period over which cash resources will be sufficient to allow Company to fund current operating plan	12 months
Equipment Lease Credit Facility
Remaining borrowing capacity	$ 1,300