Revenue Recognition - Additional Information (Detail) ¥ in Billions		1 Months Ended			3 Months Ended							12 Months Ended
	May 17, 2018 USD ($) item	Mar. 31, 2017 USD ($)	Apr. 30, 2013 USD ($) item	Apr. 30, 2012 USD ($) item	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2019 USD ($) Milestone item	Dec. 31, 2018 USD ($) Milestone	Dec. 31, 2017 USD ($) Milestone	Apr. 30, 2013 JPY (¥)	Apr. 30, 2013 USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue, current					$ 22,262,000				$ 26,825,000			$ 22,262,000	$ 26,825,000
Deferred revenue, non current									15,184,000				15,184,000
Total revenue					4,511,000	$ 5,785,000	$ 5,208,000	$ 4,382,000	5,533,000	$ 5,062,000	$ 2,874,000	$ 19,886,000	$ 13,469,000	$ 911,000
Number of milestone event probable of occurrence or achieved | Milestone												0	0	0
License and Milestone Fees [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue												$ 19,746,000	$ 13,436,000	$ 530,000
Royalty [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue from contract with customer												0
VFMCRP Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Deferred revenue, current					22,262,000				26,825,000			22,262,000	26,825,000
Deferred revenue, non current									15,184,000				15,184,000
Receivables					0				0			0	0
Other assets					0				0			0	0
Deferred revenue	$ 55,444,000				0							0
Number of combined performance obligations for revenue recognized | item	1
Number of performance obligations for revenue recognized | item	2
upfront payment	$ 50,000,000
Premium from sale of stock	$ 5,444,000
Remaining performance obligations					$ 22,262,000							$ 22,262,000
Remaining performance obligation, expected timing of satisfaction, year					2020							2020
VFMCRP Agreement [Member] | License and Milestone Fees [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue												$ 33,182,000
Maruishi and CKDP Agreements [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Receivables					$ 0				0			0	0
Other assets					0				0			0	0
Deferred revenue					0				$ 0			$ 0	$ 0
Number of license agreements | item												2
Remaining performance obligations					$ 0							$ 0
Maruishi Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of performance obligations for revenue recognized | item			2
Premium from sale of stock			$ 337,000
Upfront non-refundable, non-creditable license fee and premium from sale of stock			15,337,000
Maruishi Agreement [Member] | Clinical Development and Regulatory Milestones [Member] | Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining potential consideration																$ 10,500,000
Maruishi Agreement [Member] | One-time Sales Milestone [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining potential consideration | ¥															¥ 1
Maruishi Agreement [Member] | License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated selling price			10,200,000
Upfront payments on obligations			9,637,000
Maruishi Agreement [Member] | R&D Services [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Estimated selling price			6,200,000
Upfront payments on obligations			$ 5,700,000
CKDP Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of combined performance obligations for revenue recognized | item				1
Premium from sale of stock				$ 83,000
CKDP Agreement [Member] | Clinical Development and Regulatory Milestones [Member] | Maximum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining potential consideration				3,750,000
CKDP Agreement [Member] | License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue from contract with customer				$ 646,000
Maruishi Pharmaceutical Co., Ltd. [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of performance obligations for revenue recognized | item												2
Maruishi Pharmaceutical Co., Ltd. [Member] | License and Milestone Fees [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue														530,000
Maruishi Pharmaceutical Co., Ltd. [Member] | License [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total revenue		$ 843,000												$ 843,000