Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common Stock/Ordinary Shares	Additional paid in capital	Accumulated other comprehensive income	Accumulated deficit	Total
Stockholders' equity, beginning balance at Dec. 31, 2017	$ 367	$ 360,872	$ 27	$ (279,198)	$ 82,068
Stockholders' equity, beginning balance (in shares) at Dec. 31, 2017	36,708
Consolidated Statements of Changes in Stockholders’ Equity
Issuance of ordinary shares	$ 35	19,353			19,388
Issuance of ordinary shares (in shares)	3,526
Equity transaction costs		(916)			(916)
Stock-based compensation expense		1,244			1,244
Net loss				(13,342)	(13,342)
Stockholders' equity, ending balance at Mar. 31, 2018	$ 402	380,553	27	(292,540)	88,442
Stockholders' equity, ending balance (in shares) at Mar. 31, 2018	40,234
Stockholders' equity, beginning balance at Dec. 31, 2017	$ 367	360,872	27	(279,198)	82,068
Stockholders' equity, beginning balance (in shares) at Dec. 31, 2017	36,708
Consolidated Statements of Changes in Stockholders’ Equity
Net loss					(83,955)
Stockholders' equity, ending balance at Sep. 30, 2018	$ 665	458,887	27	(363,153)	96,426
Stockholders' equity, ending balance (in shares) at Sep. 30, 2018	66,484
Stockholders' equity, beginning balance at Mar. 31, 2018	$ 402	380,553	27	(292,540)	88,442
Stockholders' equity, beginning balance (in shares) at Mar. 31, 2018	40,234
Consolidated Statements of Changes in Stockholders’ Equity
Issuance of ordinary shares	$ 8	3,389			3,397
Issuance of ordinary shares (in shares)	725
Equity transaction costs		(152)			(152)
Stock-based compensation expense		767			767
Net loss				(17,788)	(17,788)
Stockholders' equity, ending balance at Jun. 30, 2018	$ 410	384,557	27	(310,328)	74,666
Stockholders' equity, ending balance (in shares) at Jun. 30, 2018	40,959
Consolidated Statements of Changes in Stockholders’ Equity
Issuance of ordinary shares	$ 182	49,817			49,999
Issuance of ordinary shares (in shares)	18,188
Shares issued in connection with the acquisition of Zavante Therapeutics, Inc.	$ 73	26,829			26,902
Shares issued in connection with the acquisition of Zavante Therapeutics, Inc. (in shares)	7,337
Equity transaction costs		(3,739)			(3,739)
Stock-based compensation expense		1,423			1,423
Net loss				(52,825)	(52,825)
Stockholders' equity, ending balance at Sep. 30, 2018	$ 665	458,887	27	(363,153)	96,426
Stockholders' equity, ending balance (in shares) at Sep. 30, 2018	66,484
Stockholders' equity, beginning balance at Dec. 31, 2018	$ 670	461,911	27	(393,978)	68,630
Stockholders' equity, beginning balance (in shares) at Dec. 31, 2018	67,019
Consolidated Statements of Changes in Stockholders’ Equity
Issuance of ordinary shares	$ 43	10,014			10,057
Issuance of ordinary shares (in shares)	4,317
Equity transaction costs		(270)			(270)
Stock-based compensation expense		1,907			1,907
Net loss				(20,217)	(20,217)
Stockholders' equity, ending balance at Mar. 31, 2019	$ 713	473,562	27	(414,195)	60,107
Stockholders' equity, ending balance (in shares) at Mar. 31, 2019	71,336
Stockholders' equity, beginning balance at Dec. 31, 2018	$ 670	461,911	27	(393,978)	68,630
Stockholders' equity, beginning balance (in shares) at Dec. 31, 2018	67,019
Consolidated Statements of Changes in Stockholders’ Equity
Net loss					(59,719)
Stockholders' equity, ending balance at Sep. 30, 2019	$ 780	492,105	27	(453,697)	39,215
Stockholders' equity, ending balance (in shares) at Sep. 30, 2019	77,994
Stockholders' equity, beginning balance at Mar. 31, 2019	$ 713	473,562	27	(414,195)	60,107
Stockholders' equity, beginning balance (in shares) at Mar. 31, 2019	71,336
Consolidated Statements of Changes in Stockholders’ Equity
Issuance of ordinary shares	$ 12	3,522			3,534
Issuance of ordinary shares (in shares)	1,221
Shares issued in connection with the employee stock purchase plan	$ 1	169			170
Shares issued in connection with the employee stock purchase plan (in shares)	91
Shares issued in connection with the vesting of restricted stock units	$ 3				3
Shares issued in connection with the vesting of restricted stock units (in shares)	258
Equity transaction costs		(523)			(523)
Stock-based compensation expense		1,821			1,821
Net loss				(21,707)	(21,707)
Stockholders' equity, ending balance at Jun. 30, 2019	$ 729	478,551	27	(435,902)	43,405
Stockholders' equity, ending balance (in shares) at Jun. 30, 2019	72,906
Consolidated Statements of Changes in Stockholders’ Equity
Issuance of ordinary shares	$ 41	9,555			9,596
Issuance of ordinary shares (in shares)	4,102
Shares issued in connection with the acquisition of Zavante Therapeutics, Inc.	$ 8	(8)
Shares issued in connection with the acquisition of Zavante Therapeutics, Inc. (in shares)	815
Shares issued in connection with the vesting of restricted stock units	$ 2				2
Shares issued in connection with the vesting of restricted stock units (in shares)	171
Equity transaction costs		(131)			(131)
Stock-based compensation expense		4,138			4,138
Net loss				(17,795)	(17,795)
Stockholders' equity, ending balance at Sep. 30, 2019	$ 780	$ 492,105	$ 27	$ (453,697)	$ 39,215
Stockholders' equity, ending balance (in shares) at Sep. 30, 2019	77,994