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Collaboration and Licensing Agreements - Additional Information (Detail)		3 Months Ended		6 Months Ended
	May 17, 2018 USD ($) PerformanceObligation $ / shares shares	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Mar. 20, 2019 $ / shares
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Purchase common stock per share amount \| $ / shares						$ 19.37
Revenue from contract with customer		$ 5,208,000	$ 2,874,000	$ 9,590,000	$ 2,874,000
Clinical Compound Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from contract with customer				$ 140,000
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-refundable, non-creditable upfront payment	$ 50,000,000
Common stock, shares issued \| shares	1,174,827
Purchase of common stock value	$ 20,000,000
Purchase common stock per share amount \| $ / shares	$ 17.024
Closing prices of company common stock description	over a pre-determined average closing price of the Company’s common stock.
Premium from sale of stock	$ 5,444,000
Contract liabilities	$ 55,444,000
Number of combined performance obligations for revenue recognized \| PerformanceObligation	1
Number of days to terminate agreement				60 days
Termination notice effective period				12 months
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member] \| Maximum [Member] \| Regulatory and Commercial Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable	$ 470,000,000
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member] \| Maximum [Member] \| Regulatory Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable	30,000,000
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member] \| Maximum [Member] \| Tiered Commercial Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable	$ 440,000,000
Maruishi Pharmaceutical Co., Ltd. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cost of clinical compound related to R&D expense				$ 126,000
Maruishi Pharmaceutical Co., Ltd. [Member] \| Clinical Compound Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from contract with customer				$ 140,000	$ 0