Summary of Significant Accounting Policies - Concentration of Credit Risk (Detail) - Revenue from Contract with Customer Benchmark [Member] - Customer Concentration Risk [Member]	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Vifor Fresenius Medical Care Renal Pharma Ltd. [Member]
Concentration Risk [Line Items]
Concentration of revenue percentage	67.00%	17.00%	99.00%
Vifor International Ltd. [Member]
Concentration Risk [Line Items]
Concentration of revenue percentage	25.00%	83.00%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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