Property and Equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property and equipment disclosures
Total property and equipment	$ 43,500	$ 41,934
Less: accumulated depreciation	(4,058)	(1,556)
Property and equipment, net	39,442	40,378
Depreciation expense	2,683	1,202	$ 471
Building
Property and equipment disclosures
Total property and equipment	35,167	35,941
Laboratory equipment
Property and equipment disclosures
Total property and equipment	7,415	5,130
Computer equipment
Property and equipment disclosures
Total property and equipment	550	392
Leasehold improvements
Property and equipment disclosures
Total property and equipment	177	200
Furniture and office equipment
Property and equipment disclosures
Total property and equipment	96	170
Software
Property and equipment disclosures
Total property and equipment	$ 95	$ 101