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Equity and Stock-based Compensation - Subsidiary Stock and Non-Controlling Interests - Additional information (Detail) - USD ($) $ / shares in Units, $ in Millions | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Nov. 19, 2014 | Jan. 31, 2013
Class Of Stock [Line Items] |  |  |  |
Preferred stock, shares outstanding | 0 | 0 |  |
IPO [Member] |  |  |  |
Class Of Stock [Line Items] |  |  |  |
Conversion rights, shares issued upon conversion of each preferred share |  |  | 958,996 |
FibroGen Europe [Member] |  |  |  |
Class Of Stock [Line Items] |  |  |  |
Preferred stock, shares outstanding | 42,619,022 | 42,619,022 |  |
Preferred stock redemption percentage | Redemption Right — If a Preferred Share can be redeemed by a majority shareholder owning more than ninety percent (90%) of the shares of FibroGen Europe in accordance with the provisions of the Finnish Limited Liability Companies Act, the minority holders of Preferred Shares have the right to request redemption of their shares. |  |  |
Minimum percentage of shareholder's approval to call for redemption of preferred shares | 90.00% |  |  |
Preferred stock, voting rights | one vote |  |  |
Conversion rights, shares issued upon conversion of each preferred share | 1 |  |  |
FibroGen Europe [Member] | Series A [Member] |  |  |  |
Class Of Stock [Line Items] |  |  |  |
Preferred stock, shares outstanding | 1,700,845 | 1,700,845 |  |
FibroGen Europe [Member] | Series B [Member] |  |  |  |
Class Of Stock [Line Items] |  |  |  |
Preferred stock, shares outstanding | 1,875,000 | 1,875,000 |  |
FibroGen Europe [Member] | Series C [Member] |  |  |  |
Class Of Stock [Line Items] |  |  |  |
Preferred stock, shares outstanding | 1,599,503 | 1,599,503 |  |
FibroGen Europe [Member] | Series D [Member] |  |  |  |
Class Of Stock [Line Items] |  |  |  |
Preferred stock, shares outstanding | 1,520,141 | 1,520,141 |  |
FibroGen Europe [Member] | Series E [Member] |  |  |  |
Class Of Stock [Line Items] |  |  |  |
Preferred stock, shares outstanding | 459,565 | 459,565 |  |
FibroGen Europe [Member] | Series F [Member] |  |  |  |
Class Of Stock [Line Items] |  |  |  |
Preferred stock, shares outstanding | 5,714,332 | 5,714,332 |  |
FibroGen Europe [Member] | Series G [Member] |  |  |  |
Class Of Stock [Line Items] |  |  |  |
Preferred stock, shares outstanding | 9,927,500 | 9,927,500 |  |
FibroGen Europe [Member] | Series H [Member] |  |  |  |
Class Of Stock [Line Items] |  |  |  |
Preferred stock, shares outstanding | 19,822,136 | 19,822,136 |  |
FibroGen Cayman [Member] |  |  |  |
Class Of Stock [Line Items] |  |  |  |
Conversion rights, shares issued upon conversion of each preferred share | 1 |  |  |
Convertible promissory note | $ 0.7 | $ 0.7 |  | $ 0.6
Convertible promissory note interest rate | 2.00% |  |  |
Conditions of payment of interest, convertible promissory note | 0 |  |  |
FibroGen Cayman [Member] | Series A [Member] |  |  |  |
Class Of Stock [Line Items] |  |  |  |
Preferred stock, shares outstanding | 6,758,000 | 6,758,000 |  |
Preferred shares issued, price per share | $ 1.00 |  |  |
Cash dividend percentage | 6.00% |  |  |

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