Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Private Placement	Direct Registered Offering	At The Market Offering Program	Convertible Preferred Stock	Common Stock	Common Stock Private Placement	Common Stock Direct Registered Offering	Common Stock At The Market Offering Program	Common Stock Holders of Mirax	Additional Paid-in Capital	Additional Paid-in Capital Private Placement	Additional Paid-in Capital Direct Registered Offering	Additional Paid-in Capital At The Market Offering Program	Accumulated Deficit
Balance at Dec. 31, 2014	$ (150,623)					$ 9					$ 1,414				$ (152,046)
Temporary equity balance , shares at Dec. 31, 2014					27,654,928
Temporary equity balance at Dec. 31, 2014					$ 145,110
Balance, shares at Dec. 31, 2014						907,037
Issuance of common stock from option exercises	24										24
Issuance of common stock from option exercises, shares						31,427
Stock-based compensation	1,066										1,066
Issuance of Series C convertible preferred stock (net of issuance costs of $221)					$ 15,729
Issuance of Series C convertible preferred stock (net of issuance costs of $221), shares					2,727,059
Conversion of convertible securities, value	160,839				$ (160,839)	$ 304					160,535
Conversion of convertible securities, shares					(30,381,987)	30,381,987
Issuance of common stock, value		$ 26,323					$ 59					$ 26,264
Issuance of common stock, shares							5,884,504			1,000,005
Conversion of convertible preferred stock warrants into common stock warrants in connection with the Merger	93										93
Issuance of common stock warrants to placement agent as payment for services	316										316
Net loss	(44,995)														(44,995)
Balance at Dec. 31, 2015	(6,957)					$ 372					189,712				(197,041)
Balance, shares at Dec. 31, 2015						38,204,960
Issuance of common stock from option exercises	539					$ 8					531
Issuance of common stock from option exercises, shares						773,718
Stock-based compensation	2,907										2,907
Issuance of common stock, value		10,494					$ 46					10,448
Issuance of common stock, shares							4,602,506
Net loss	(50,636)														(50,636)
Balance at Dec. 31, 2016	(43,653)					$ 426					203,598				(247,677)
Balance, shares at Dec. 31, 2016						43,581,184
Issuance of common stock from option exercises	$ 665					$ 4					661
Issuance of common stock from option exercises, shares	420,377					420,377
Issuance of common stock from releases of restricted stock units, shares						57,626
Stock-based compensation	$ 5,319										5,319
Issuance of common stock, value		$ 22,616	$ 49,860	$ 38,979			$ 86	$ 84	$ 66			$ 22,530	$ 49,776	$ 38,913
Issuance of common stock, shares				0			8,602,589	8,382,643	6,575,062
Issuance of common stock from warrant exercises	103										103
Issuance of common stock from warrant exercises, shares						34,493
Reclassification of warrant liability to additional paid-in capital upon warrant exercises	274										274
Net loss	(72,176)														(72,176)
Balance at Dec. 31, 2017	$ 1,987					$ 666					$ 321,174				$ (319,853)
Balance, shares at Dec. 31, 2017						67,653,974