Business (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended			48 Months Ended
	Sep. 30, 2015	Jul. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Sep. 30, 2014	Dec. 31, 2012
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net cash used for operating activities			$ 25,183	$ 12,879	$ 4,734	$ 44,900
Schedule of Capitalization, Equity [Line Items]
Cash and cash equivalents	$ 126,467		$ 126,467	$ 48,555	$ 8,629	$ 126,467	$ 48,555	$ 3,405
Underwriting Agreement [Member]
Schedule of Capitalization, Equity [Line Items]
Proceeds from the underwriting agreement, including additional shares sold, net of cost	$ 104,600	$ 53,100