Property and Equipment Net - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment [Line Items]
Total property and equipment	$ 9,948	$ 618
Accumulated depreciation and amortization	(624)	(80)
Property and equipment, net	9,324	538
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	1,038	458
Lab Equipment [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	2,780
Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	1,213	105
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	$ 4,917	$ 55