XML 40 R30.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Collaboration Agreements - Summary of Revenue Recognized Under the Collaboration Agreements - Additional Information 4 (Detail) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2018 USD ($)
Japan [Member] |
Revenue Recognition, Multiple-deliverable Arrangements [Line Items] |
Remainder of transaction price, variable consideration from estimated future co-development billing | $ 2.8
Europe [Member] |
Revenue Recognition, Multiple-deliverable Arrangements [Line Items] |
Remainder of transaction price, variable consideration from estimated future co-development billing | 27.4
U.S./RoW and China [Member] |
Revenue Recognition, Multiple-deliverable Arrangements [Line Items] |
Remainder of transaction price, variable consideration from estimated future co-development billing | $ 284.1

X
- Definition Variable consideration payment received from estimated future co-development billing. + References No definition available. + Details
Name: | fgen_VariableConsiderationPaymentReceivedFromEstimatedFutureCoDevelopmentBilling
Namespace Prefix: | fgen_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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_RevenueRecognitionMultipleDeliverableArrangementsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_StatementGeographicalAxis=country_JP
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=us-gaap_EuropeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementGeographicalAxis=fgen_UnitedStatesRestOfWorldAndChinaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |