Related Party Transactions (Detail)	1 Months Ended			12 Months Ended
	Feb. 28, 2018 shares	Jun. 30, 2017 shares	Mar. 31, 2017 USD ($)	Dec. 31, 2018 shares	Dec. 31, 2017 shares
Series N Preferred Stock
Related Party Transaction [Line Items]
Stock Issued (in shares)		22,500
Number of shares converted (in shares)		21,925
BVF Partners, L.P. | Series N Preferred Stock
Related Party Transaction [Line Items]
Number of shares converted (in shares)	575
BVF Partners, L.P. | Series O Preferred Stock
Related Party Transaction [Line Items]
Conversion of stock (in shares)	12,575
Affiliated Entity | BVF Partners, L.P.
Related Party Transaction [Line Items]
Common stock owned by others, percentage				12.00%	20.00%
Affiliated Entity | BVF Partners, L.P. | Series N Preferred Stock
Related Party Transaction [Line Items]
Stock Issued (in shares)		6,750
Number of shares converted (in shares)		6,175
Conversion of stock (in shares)		4,100,000
Aequus Biopharma, Inc | Affiliated Entity | License And Promissory Note Termination, And Note Cancellation Agreements
Related Party Transaction [Line Items]
Amount funded to subsidiary | $			$ 347,500
Percent of milestone payments to be received			0.2
Milestone payments to be received | $			$ 20,000,000
Percentage of royalty payable to net sales			5.00%
Period from first commercial sale			10 years
License And Promissory Note | Convertible Debt | Aequus Biopharma, Inc | Affiliated Entity
Related Party Transaction [Line Items]
Debt cancelled and terminated | $			$ 13,700,000
Common Stock
Related Party Transaction [Line Items]
Stock Issued (in shares)	23,000,000			23,000,000
Conversion of stock (in shares)				(8,000,000)	14,616,000
Common Stock | Series N Preferred Stock
Related Party Transaction [Line Items]
Conversion of stock (in shares)		14,600,000
Common Stock | BVF Partners, L.P.
Related Party Transaction [Line Items]
Stock Issued (in shares)	6,300,000
Number of shares converted (in shares)	8,000,000