Property and Equipment Net - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Property Plant And Equipment [Line Items]
Total property and equipment	$ 12,239	$ 9,948
Accumulated depreciation and amortization	(1,178)	(624)
Property and equipment, net	11,061	9,324
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	1,167	1,038
Lab Equipment [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	4,866	2,780
Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	1,251	1,213
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	$ 4,955	$ 4,917