XML 100 R79.htm IDEA: XBRL DOCUMENT
v3.22.4

Product Development Obligations - Additional Information (Detail) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2022 USD ($) DevelopmentObligation | Dec. 31, 2021 USD ($)
Debt Instrument [Line Items] |  |
Number of product development obligations | DevelopmentObligation | 11 |
Accrued product development costs excluding interest | $ 10.1 | $ 10.7
Accrued Interest | $ 6.8 | $ 6.9
Bank of Finland Interest Rate [Member] |  |
Debt Instrument [Line Items] |  |
Percentage points deducted to reference rate to compute effective interest rate | 1.00% |
Minimum [Member] |  |
Debt Instrument [Line Items] |  |
Interest rate on product development advances | 3.00% |

X
- Definition Accrued Product Development Costs Excluding Interest. + References No definition available. + Details
Name: | fgen_AccruedProductDevelopmentCostsExcludingInterest
Namespace Prefix: | fgen_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Number of product development obligations. + References No definition available. + Details
Name: | fgen_NumberOfProductDevelopmentObligations
Namespace Prefix: | fgen_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 1B -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DebtInstrumentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of interest payable on debt, including, but not limited to, trade payables. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.15(5)) -URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.15(a)) -URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910 + Details
Name: | us-gaap_InterestPayableCurrentAndNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Percentage added to reference rate used to compute variable rate on loan receivable. + References No definition available. + Details
Name: | us-gaap_LoansReceivableBasisSpreadOnVariableRate
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_VariableRateAxis=fgen_BankOfFinlandInterestRateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |