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Collaboration and Licensing Agreements - Additional Information (Detail)			3 Months Ended	6 Months Ended
	May 18, 2018 shares	May 17, 2018 USD ($) PerformanceObligation $ / shares shares	Jun. 30, 2018 USD ($)	Jun. 30, 2018 USD ($) PerformanceObligation	Jun. 30, 2017 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from contract with customer			$ 2,874,000	$ 2,874,000	$ 911,000
License and Milestone Fees [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from contract with customer			$ 2,874,000	$ 2,874,000	530,000
Collaborative Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from contract with customer					313,000
Clinical Compound Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from contract with customer					68,000
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of performance obligations for revenue recognized \| PerformanceObligation				2
Non-refundable, non-creditable upfront payment		$ 50,000,000
Common stock, shares issued \| shares	1,174,827	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]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Third-party cost for clinical development		$ 20,000,000
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]
Number of performance obligations for revenue recognized \| PerformanceObligation				2
Cost of clinical compound related to R&D expense				$ 0	61,000
Maruishi Pharmaceutical Co., Ltd. [Member] \| Sub-License Fee [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from contract with customer					843,000
Maruishi Pharmaceutical Co., Ltd. [Member] \| License and Milestone Fees [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from contract with customer					530,000
Maruishi Pharmaceutical Co., Ltd. [Member] \| Collaborative Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from contract with customer					313,000
Maruishi Pharmaceutical Co., Ltd. [Member] \| Clinical Compound Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from contract with customer				$ 0	$ 68,000