XML 69 R60.htm IDEA: XBRL DOCUMENT
v3.25.3

Commitments and Contingencies - Additional Information (Detail) $ in Thousands | 1 Months Ended | 2 Months Ended |  |
--- | --- | --- | --- | ---
May 31, 2025 USD ($) | May 31, 2021 PutativeClassAction | Sep. 30, 2025 USD ($) | Oct. 17, 2023 USD ($)
Commitments And Contingencies [Line Items] |  |  |  |
Number of complaints filed | PutativeClassAction |  | 5 |  |
Litigation settlement amount |  |  |  | $ 28,500
Civil penalty payment | $ 1,250 |  |  |
General Purchases And Other Programs [Member] |  |  |  |
Commitments And Contingencies [Line Items] |  |  |  |
Recorded unconditional purchase obligation |  |  | $ 4,000 |
Manufacture and Supply of Roxadustat [Member] |  |  |  |
Commitments And Contingencies [Line Items] |  |  |  |
Recorded unconditional purchase obligation |  |  | $ 2,600 |

X
- Definition Commitments and contingencies. + References No definition available. + Details
Name: | fgen_CommitmentsAndContingenciesLineItems
Namespace Prefix: | fgen_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Loss contingency, civil penalty payment. + References No definition available. + Details
Name: | fgen_LossContingencyCivilPenaltyPayment
Namespace Prefix: | fgen_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of loss contingency liability. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 450 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483076/450-20-50-1 Reference 2: http://www.xbrl.org/2003/role/recommendedDisclosureRef -Topic 450 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483076/450-20-50-10 + Details
Name: | us-gaap_LossContingencyAccrualAtCarryingValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The total number of new claims filed pertaining to a loss contingency during the period. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 450 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483076/450-20-50-4 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 450 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 9 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483076/450-20-50-9 + Details
Name: | us-gaap_LossContingencyNewClaimsFiledNumber
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of the recorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 440 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482648/440-10-50-6 + Details
Name: | us-gaap_RecordedUnconditionalPurchaseObligation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=fgen_GeneralPurchasesAndOtherProgramsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=fgen_ManufactureAndSupplyOfRoxadustatMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |