Business (Details) - USD ($) $ in Thousands	1 Months Ended		9 Months Ended		45 Months Ended
	Sep. 30, 2015	Jul. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net cash used for operating activities			$ 16,702	$ 7,475	$ 36,500
Schedule of Capitalization, Equity [Line Items]
Cash and cash equivalents	$ 135,055		$ 135,055	$ 54,131	$ 135,055	$ 48,555	$ 8,629
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