Supplementary Balance Sheet Information - Property and Equipment (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 969,833	$ 378,711	$ 234,813
Property and equipment	5,588,900	3,545,361
Less—accumulated depreciation and amortization	(1,761,985)	(854,782)
Property and equipment, net	3,826,915	2,690,579
Furniture And Office Equipment
Property, Plant and Equipment [Line Items]
Property and equipment	1,144,741	1,264,547
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	1,994,514	39,401
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment	$ 2,449,645	$ 2,241,413