Warrant Liability - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Warrant Liability [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements		$ (175)
Warrants 2016 [Member]
Warrant Liability [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights			6,398
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	$ 200
Extinguishment of Debt, Amount	400
Increase (Decrease) in Derivative Liabilities	$ 0	$ 2,400
Health care Institutional Investors
Warrant Liability [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights				14,706
Class of Warrant or Right, Exercise Price of Warrants or Rights				$ 460.00
Hc Wainwright Co Llc
Warrant Liability [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights				1,250
Class of Warrant or Right, Exercise Price of Warrants or Rights				$ 492.00