Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Initial Public Offering	Genethon	Convertible Preferred Stock, Series Seed	Convertible Preferred Stock, Series A	Convertible Preferred Stock, Series B	Convertible Preferred Stock, Series C	Common Stock	Common Stock Initial Public Offering	Common Stock Genethon	Additional Paid-in Capital	Additional Paid-in Capital Initial Public Offering	Additional Paid-in Capital Genethon	Accumulated Deficit	Accumulated Other Comprehensive Loss
Balance at Dec. 31, 2013	$ 12,912			$ 1,378	$ 13,759						$ 1,241			$ (3,466)
Balance (in shares) at Dec. 31, 2013				627,867	2,511,435			498,704
Issuance of common stock			$ 336										$ 336
Issuance of common stock, shares										262,396
Issuance of convertible preferred stock, net in issuance costs					$ 14,998	$ 42,268
Issuance of convertible preferred stock, net in issuance costs, shares					2,511,441	3,796,635
Stock-based compensation expense	179										179
Net loss	(10,819)													(10,819)
Other comprehensive loss	(10)
Balance at Dec. 31, 2014	59,864			$ 1,378	$ 28,757	$ 42,268					1,756			(14,285)	$ (10)
Balance (in shares) at Dec. 31, 2014				627,867	5,022,876	3,796,635		761,100
Issuance of common stock for acquisition of business	3,575										3,575
Issuance of common stock for acquisition of business, shares								1,293,058
Exercise of stock options	$ 70										70
Exercise of stock options, shares	51,994							51,994
Issuance of Series B convertible preferred stock, for acquisition of business	$ 567					$ 567
Issuance of Series B convertible preferred stock, for acquisition of business, shares						46,969
Issuance of convertible preferred stock, net in issuance costs	62,780						$ 62,780
Issuance of convertible preferred stock, net in issuance costs, shares							4,325,954
Stock-based compensation expense	1,291										1,291
Net loss	(26,458)													(26,458)
Balance at Dec. 31, 2015	101,689			$ 1,378	$ 28,757	$ 42,835	$ 62,780				6,692			(40,743)	(10)
Balance (in shares) at Dec. 31, 2015				627,867	5,022,876	3,843,604	4,325,954	2,106,152
Issuance of common stock		$ 75,208										$ 75,208
Issuance of common stock, shares									5,675,000
Exercise of stock options	$ 157										157
Exercise of stock options, shares	129,809							129,806
Stock-based compensation expense	$ 2,004										2,004
Preferred stock conversion to common stock				$ (1,378)	$ (28,757)	$ (42,835)	$ (62,780)				135,750
Preferred stock conversion to common stock, shares				(627,867)	(5,022,876)	(3,843,604)	(4,325,954)	13,820,301
Net loss	(59,668)													(59,668)
Other comprehensive loss	(19)														(19)
Balance at Dec. 31, 2016	$ 119,371										$ 219,811			$ (100,411)	$ (29)
Balance (in shares) at Dec. 31, 2016								21,731,259