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v3.25.3

Future Policy Benefits - Schedule of Additional Information, Cohort NPR (Details) $ in Millions | 9 Months Ended
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Sep. 30, 2025 USD ($)
Insurance [Abstract] |
NPR before capping | 105.00%
Reserves before NPR capping | $ 1,158
Reserves after NPR capping | 1,172
Loss Expense | $ 14

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- Definition Net Premium Ratio Before Capping + References No definition available. + Details
Name: | fnf_NetPremiumRatioBeforeCapping
Namespace Prefix: | fnf_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

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- Definition Premium Loss Expense, Net + References No definition available. + Details
Name: | fnf_PremiumLossExpenseNet
Namespace Prefix: | fnf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Reserves After NP Ratio Capping + References No definition available. + Details
Name: | fnf_ReservesAfterNPRatioCapping
Namespace Prefix: | fnf_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Reserves Before NP Ratio Capping + References No definition available. + Details
Name: | fnf_ReservesBeforeNPRatioCapping
Namespace Prefix: | fnf_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- References No definition available. + Details
Name: | us-gaap_InsuranceAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration