Property and Equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 25,156	$ 21,319
Less: Accumulated depreciation	(10,227)	(8,968)
Property and equipment, net	$ 14,929	12,351
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment, useful lives (Years)	3 years
Property and equipment, gross	$ 6,687	4,670
Computer Equipment and Software
Property Plant And Equipment [Line Items]
Property and equipment, useful lives (Years)	3 years
Property and equipment, gross	$ 2,529	2,703
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	228	193
Equipment Acquired Under Capital Leases
Property Plant And Equipment [Line Items]
Property and equipment, gross	6,172	6,165
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 9,540	$ 7,588
Property and equipment, useful lives	Shorter of lease term or economic life
Minimum | Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, useful lives (Years)	3 years
Minimum | Equipment Acquired Under Capital Leases
Property Plant And Equipment [Line Items]
Property and equipment, useful lives (Years)	3 years
Maximum | Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, useful lives (Years)	7 years
Maximum | Equipment Acquired Under Capital Leases
Property Plant And Equipment [Line Items]
Property and equipment, useful lives (Years)	5 years