Significant Accounting Policies - Additional Information (Detail)	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2020 USD ($) $ / shares shares	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($) shares	Jun. 30, 2020 USD ($) Segment $ / shares shares	Jun. 30, 2019 USD ($) shares	Dec. 31, 2019 USD ($)	Dec. 31, 2017 USD ($)
Significant Accounting Policies [Line Items]
Number of segments | Segment				1
Incremental costs expenses	$ 0		$ 0	$ 0	$ 0
License revenue recognized	70,582,000		53,919,000	121,799,000	152,986,000
Restricted cash	12,200,000			12,200,000		$ 13,200,000
Cash and cash equivalents and restricted cash in excess of insured limits	103,400,000			103,400,000
Allowance for doubtful accounts	$ 0		$ 0	$ 0	0
Research and development expense related to inventory							$ 4,500,000
Lessee, operating lease, existence of option to extend				true
Lessee, operating lease, option to extend, description				Options to extend or terminate a lease are considered in the lease term to the extent that the option is reasonably certain of exercise
Lessee, operating lease, existence of option to terminate				true
Lessee, operating lease, option to terminate, description				Options to extend or terminate a lease are considered in the lease term to the extent that the option is reasonably certain of exercise
Average incremental borrowing rate	10.90%			10.90%
Reduction in carrying value of right of use asset						$ 1,200,000
Amortization expenses related to intangible assets	$ 1,300,000			$ 2,300,000
Estimated future amortization expense related to intangible assets, remainder of 2020	4,000,000.0			4,000,000.0
Estimated future amortization expense related to intangible assets, 2021	8,000,000.0			8,000,000.0
Estimated future amortization expense related to intangible assets, 2022	8,000,000.0			8,000,000.0
Estimated future amortization expense related to intangible assets, 2023	8,000,000.0			8,000,000.0
Estimated future amortization expense related to intangible assets, 2024	8,000,000.0			8,000,000.0
Estimated future amortization expense related to intangible assets, 2025	8,000,000.0			8,000,000.0
Estimated future amortization expense related to intangible assets, 2026	8,000,000.0			8,000,000.0
Estimated future amortization expense related to intangible assets, 2027	8,000,000.0			8,000,000.0
Estimated future amortization expense related to intangible assets, 2028	8,000,000.0			8,000,000.0
Estimated future amortization expense related to intangible assets, 2029	8,000,000.0			8,000,000.0
Estimated future amortization expense related to intangible assets, 2030	2,000,000.0			$ 2,000,000.0
Computer Hardware and Software
Significant Accounting Policies [Line Items]
Estimated useful lives				3 years
Phone Equipment
Significant Accounting Policies [Line Items]
Estimated useful lives				3 years
Furniture and Fixtures
Significant Accounting Policies [Line Items]
Estimated useful lives				7 years
Letter of Credit
Significant Accounting Policies [Line Items]
Lease Expiration Year				2026
License Revenue
Significant Accounting Policies [Line Items]
License revenue recognized	20,700,000			$ 22,700,000	$ 53,500,000
Bixink Therapeutics Co Ltd | License Revenue
Significant Accounting Policies [Line Items]
License revenue recognized	500,000
Bixink Therapeutics Co Ltd | License Agreement
Significant Accounting Policies [Line Items]
Potential milestone payments	5,500,000			5,500,000
CANbridge Life Sciences | License Revenue
Significant Accounting Policies [Line Items]
License revenue recognized	20,000,000.0
CANbridge Life Sciences | License Agreement
Significant Accounting Policies [Line Items]
Potential milestone payments	195,000,000.0			195,000,000.0
Medison Pharma Ltd | License Revenue
Significant Accounting Policies [Line Items]
License revenue recognized	200,000
Medison Pharma Ltd | License Agreement
Significant Accounting Policies [Line Items]
Potential milestone payments	300,000			300,000
Pint Pharma International SA | License Revenue
Significant Accounting Policies [Line Items]
License revenue recognized		$ 2,500,000
Pint Pharma International SA | License Agreement
Significant Accounting Policies [Line Items]
Potential milestone payments	20,000,000.0			20,000,000.0
Knight Therapeutics, Inc | License Agreement
Significant Accounting Policies [Line Items]
Potential milestone payments	5,400,000			5,400,000
Pierre Fabre Medicament SAS | License Agreement
Significant Accounting Policies [Line Items]
Potential milestone payments	$ 348,000,000.0			$ 348,000,000.0
Minimum
Significant Accounting Policies [Line Items]
Revenue recognition, payment terms				10 days
Maximum
Significant Accounting Policies [Line Items]
Revenue recognition, payment terms				68 days
Amortization period recognized				1 year
Common Stock
Significant Accounting Policies [Line Items]
Shares of common stock that could be acquired by warrant | shares	2,116,250			2,116,250
Common stock price | $ / shares	$ 16			$ 16
Employee Stock Option
Significant Accounting Policies [Line Items]
Anti-dilutive securities excluded from the calculation of diluted earnings per share | shares	4,930,672		5,291,407	5,172,638	5,291,407
Warrants
Significant Accounting Policies [Line Items]
Anti-dilutive securities excluded from the calculation of diluted earnings per share | shares	2,116,250		2,116,250	2,116,250	2,116,250
Restricted Stock Units
Significant Accounting Policies [Line Items]
Anti-dilutive securities excluded from the calculation of diluted earnings per share | shares	1,290,442		1,905,241	2,316,621	1,905,241