Investments - Schedule of Residential Loans Segregated by Aging of Loans (By Year of Origination) and Non-accrual Loans by Amortized Cost (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Amortized Cost of Non-Accrual Loans [Abstract]
Amortized cost of loans on non-accrual	$ 76	$ 94
Residential Mortgage
Credit Quality Indicator Current Year [Abstract]
Year one	620	614
Year two	773	376
Year three	374	928
Year four	884	840
Year five	798	176
Prior	481	340
Total	3,930	3,274
Credit Quality Indicator Prior Year [Abstract]
Year one	620	614
Year two	773	376
Year three	374	928
Year four	884	840
Year five	798	176
Prior	481	340
Total	3,930	3,274
Amortized Cost of Non-Accrual Loans [Abstract]
Amortized cost of loans on non-accrual	67	85
Commercial Mortgage
Credit Quality Indicator Current Year [Abstract]
Total	3,085	2,722
Credit Quality Indicator Prior Year [Abstract]
Total	3,085	2,722
Amortized Cost of Non-Accrual Loans [Abstract]
Amortized cost of loans on non-accrual	9	9
Current (less than 30 days past due) \| Residential Mortgage
Credit Quality Indicator Current Year [Abstract]
Year one	619	610
Year two	765	368
Year three	370	911
Year four	866	805
Year five	773	162
Prior	437	312
Total	3,830	3,168
Credit Quality Indicator Prior Year [Abstract]
Year one	619	610
Year two	765	368
Year three	370	911
Year four	866	805
Year five	773	162
Prior	437	312
Total	3,830	3,168
30-89 days past due \| Residential Mortgage
Credit Quality Indicator Current Year [Abstract]
Year one	1	1
Year two	5	6
Year three	2	4
Year four	6	6
Year five	5	1
Prior	14	3
Total	33	21
Credit Quality Indicator Prior Year [Abstract]
Year one	1	1
Year two	5	6
Year three	2	4
Year four	6	6
Year five	5	1
Prior	14	3
Total	33	21
90 days or more past due \| Residential Mortgage
Credit Quality Indicator Current Year [Abstract]
Year one	0	3
Year two	3	2
Year three	2	13
Year four	12	29
Year five	20	13
Prior	30	25
Total	67	85
Credit Quality Indicator Prior Year [Abstract]
Year one	0	3
Year two	3	2
Year three	2	13
Year four	12	29
Year five	20	13
Prior	30	25
Total	$ 67	$ 85

Amortized Cost of Non-Accrual Loans

No definition available.

Name:	fnf_AmortizedCostOfNonAccrualLoansAbstract
Namespace Prefix:	fnf_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Credit Quality Indicator Current Year

+ References

No definition available.

+ Details

Name:	fnf_CreditQualityIndicatorCurrentYearAbstract
Namespace Prefix:	fnf_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Credit Quality Indicator Prior Year

+ References

No definition available.

+ Details

Name:	fnf_CreditQualityIndicatorPriorYearAbstract
Namespace Prefix:	fnf_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-3B

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-5

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable on nonaccrual status. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-16

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrual
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable originated more than five years prior to current fiscal year. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 79
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479294/326-20-55-79

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-3B

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable originated four years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable originated three years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable originated in current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable originated two years prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest of financing receivable originated in fiscal year prior to current fiscal year. Excludes net investment in lease.

+ References

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivables1To29DaysPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=fnf_FinancialAsset30To89DaysPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: