Consolidated Statements of Changes in Stockholders' Equity (Deficit) - USD ($) shares in Thousands, $ in Thousands	Common Stock/Ordinary Shares Kreos Loan 2014 Call Options	Common Stock/Ordinary Shares Options	Common Stock/Ordinary Shares	Treasury Shares Options	Treasury Shares	Additional paid in capital IPO	Additional paid in capital April 2015 Financing	Additional paid in capital Kreos Loan 2014 Call Options	Additional paid in capital Options	Additional paid in capital	Accumulated other comprehensive income (loss)	Accumulated deficit	IPO	April 2015 Financing	Kreos Loan 2014 Call Options	Options	Total
Stockholders' equity, beginning balance at Dec. 31, 2014			$ 432		$ (25)					$ 89,295	$ 1,871	$ (120,587)					$ (29,014)
Stockholders' equity, beginning balance (in shares) at Dec. 31, 2014			328		3
Consolidated Statements of Changes in Stockholders' Equity (Deficit)
Issuance of common stock			$ 1,725							149,218							150,943
Issuance of common stock (in shares)			1,563
Conversion of convertible loans			$ 222							22,519							22,741
Conversion of convertible loans (in shares)			204
Conversion of silent partnerships			$ 17							2,733							2,750
Conversion of silent partnerships (in shares)			15
Exercise of stock options	$ 10	$ 1						$ 1,420	$ 124						$ 1,430	$ 125
Exercise of stock options (in shares)	9	1
Equity transaction costs						$ (13,616)	$ (1,313)						$ (13,616)	$ (1,313)
Stock based compensation expense										1,249							1,249
Beneficial conversion feature of silent partnership										2,561							2,561
Adjustment to redemption value of silent partnership												(3,875)					(3,875)
Beneficial conversion feature of convertible loans										18,993							18,993
Extension of CLA repayment date - Modification										738							738
Unrealized loss on available-for-sale securities											(68)						(68)
Other comprehensive loss, net of tax																	1,958
Cumulative translation adjustment, net of tax											2,026						2,026
Net loss												(46,964)					(46,964)
Stockholders' equity, ending balance at Dec. 31, 2015			$ 2,407		$ (25)					273,921	3,829	(171,426)					108,706
Stockholders' equity, ending balance (in shares) at Dec. 31, 2015			2,120		3
Carrying amount as of beginning of year at Dec. 31, 2014																	634
Investment from Silent Partnership
Issuance of Silent Partnership Agreement, net of transaction fees																	962
Conversion of silent partnerships																	(2,750)
Beneficial conversion feature of silent partnership																	(2,561)
Adjustment to redemption value of silent partnership																	3,875
Cumulative translation adjustment, net of tax																	(160)
Carrying amount as of end of year at Dec. 31, 2015																	0
Total Equity, beginning balance at Dec. 31, 2014																	(28,380)
Increase (Decrease) in Combined Equity [Rollforward]
Cumulative translation adjustment, net of tax																	1,866
Total Equity, ending balance at Dec. 31, 2015																	108,706
Consolidated Statements of Changes in Stockholders' Equity (Deficit)
Change in functional currency			$ (99)		$ 3					(17,509)	(3,869)	21,474
Stockholders' equity, adjusted balance			2,308		$ (22)					256,412	(40)	(149,952)					108,706
Issuance of common stock			$ 618							24,204							24,822
Issuance of common stock (in shares)			588
Exercise of stock options		$ 13		$ 22					$ 235							$ 270
Exercise of stock options (in shares)		12		(3)
Equity transaction costs										(4,247)							(4,247)
Stock based compensation expense										2,545							2,545
Other comprehensive loss, net of tax											50						50
Net loss												(54,890)					(54,890)
Stockholders' equity, ending balance at Dec. 31, 2016			$ 2,939							279,149	10	(204,842)					77,256
Stockholders' equity, ending balance (in shares) at Dec. 31, 2016			2,720
Consolidated Statements of Changes in Stockholders' Equity (Deficit)
Issuance of common stock			$ 94							79,906							80,000
Issuance of common stock (in shares)			9,412
Exercise of stock options			$ 3							51							54
Exercise of stock options (in shares)			54
Equity transaction costs										(6,635)							(6,635)
Redomiciliation share exchange			$ (2,669)							2,669
Redomiciliation share exchange (in shares)			24,522
Stock based compensation expense										5,732							5,732
Other comprehensive loss, net of tax											17						17
Net loss												(74,356)					(74,356)
Stockholders' equity, ending balance at Dec. 31, 2017			$ 367							$ 360,872	$ 27	$ (279,198)					$ 82,068
Stockholders' equity, ending balance (in shares) at Dec. 31, 2017			36,708