Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Significant Accounting Policies [Line Items]
Reduction to research and development expenses	$ 100	$ 900
Accounts receivable	31	$ 492
ISU Abxis
Significant Accounting Policies [Line Items]
Accounts receivable	$ 10
Computer equipment
Significant Accounting Policies [Line Items]
Estimated useful lives	3 years
Laboratory and office equipment | Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives	3 years
Laboratory and office equipment | Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives	7 years
Furniture | Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives	3 years
Furniture | Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives	7 years
Leasehold improvements | Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives	3 years
Leasehold improvements | Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives	7 years