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Business - Additional Information (Detail) $ in Thousands |  |  | 1 Months Ended | 2 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | ---
Dec. 19, 2024 | Jun. 14, 2024 | Jan. 31, 2024 | Dec. 31, 2023 USD ($) | Dec. 31, 2024 USD ($) item shares | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) | Dec. 17, 2024 USD ($) | Dec. 31, 2021 USD ($)
Nature Of Business [Line Items] |  |  |  |  |  |  |  |  |
Date of formation |  |  |  |  | Jul. 02, 2004 |  |  |  |
Restructuring and related cost, percentage of workforce reduction |  | 70.00% | 50.00% |  |  |  |  |  |
Proceeds from equity and debt financing |  |  |  |  | $ 520,700 |  |  |  |
Number of follow-on public offerings | item |  |  |  |  | 4 |  |  |  |
Net proceeds from the royalty purchase and sale agreement |  |  |  |  |  | $ 36,474 |  |  |
Unrestricted cash and cash equivalents and marketable securities |  |  |  |  | $ 37,903 |  |  |  |
Accumulated deficit |  |  |  | $ 684,745 | 755,612 | 684,745 |  |  |
Net loss |  |  |  |  | (70,867) | (118,513) | $ (85,474) |  |
Net cash used in operating activities |  |  |  |  | $ (60,917) | (92,078) | (78,730) |  |
Reverse stock split ratio approval | 0.083 |  |  |  |  |  |  |  |
Reverse stock split fractional shares issued | shares |  |  |  |  | 0 |  |  |  |
Stockholders' equity |  |  |  | 57,085 | $ (4,593) | 57,085 | $ 158,779 |  | $ 227,522
Vifor Fresenius Medical Care Renal Pharma Ltd Agreement [Member] |  |  |  |  |  |  |  |  |
Nature Of Business [Line Items] |  |  |  |  |  |  |  |  |
Asset Purchase Agreement |  |  |  |  |  |  |  | $ 900 |
HCR Agreement [Member] |  |  |  |  |  |  |  |  |
Nature Of Business [Line Items] |  |  |  |  |  |  |  |  |
Net proceeds from the royalty purchase and sale agreement |  |  |  | 36,474 |  | 36,474 |  |  |
License Agreement with Maruishi Pharmaceutical Co. Ltd [Member] |  |  |  |  |  |  |  |  |
Nature Of Business [Line Items] |  |  |  |  |  |  |  |  |
Earned milestone payment |  |  |  | $ 1,449 |  | $ 1,449 |  |  |
CSL Vifor, Maruishi and CKDP | License and supply agreements for difelikefalin [Member] |  |  |  |  |  |  |  |  |
Nature Of Business [Line Items] |  |  |  |  |  |  |  |  |
Amounts earned in connection with license and supply agreements |  |  |  |  | 289,900 |  |  |  |
Affiliated Entity [Member] | Vifor International Ltd. [Member] |  |  |  |  |  |  |  |  |
Nature Of Business [Line Items] |  |  |  |  |  |  |  |  |
Proceeds from the sale of common stock under license agreement with Vifor International |  |  |  |  | $ 98,000 |  |  |  |

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