Related Party Transactions (Detail)		1 Months Ended		12 Months Ended
	Mar. 12, 2020 shares	Feb. 28, 2018 shares	Mar. 31, 2017 USD ($)	Dec. 31, 2018 shares	Dec. 31, 2019
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 convertible 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]
percentage of common stock owned by others				12.00%	12.00%
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)
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
Subsequent Event | Series X preferred Stock
Related Party Transaction [Line Items]
Number of shares converted (in shares)	0
Rights Offering | Subsequent Event | Series X preferred Stock
Related Party Transaction [Line Items]
Sale of stock (in shares)	4,429
Shares available for future conversion (in shares)	44,300,000
Rights Offering | Subsequent Event | BVF Partners, L.P. | Series X preferred Stock
Related Party Transaction [Line Items]
Number of shares converted (in shares)	0
Sale of stock (in shares)	3,047
Shares available for future conversion (in shares)	30,500,000