Fair Value of Financial Instruments - Changes to Fair Value of Financial Instruments Level 3 (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fixed maturity securities available-for-sale:
Balance at Beginning of Period	$ 2,920	$ 128	$ 138
F&G Acquisition			2,754
Assets, Total Gains (Losses) Included in Earnings	1	4	(63)	$ 16
Assets, Total Gains (Losses) Included in AOCI	46	0	68	(1)
Assets, Purchases	128	1	220	6
Assets, Sales	1	0	(1)	(1)
Assets, Settlements	(154)	0	(177)	0
Assets, Net transfer In (Out) of Level 3	(90)	0	(89)	(5)
Balance at End of Period	2,850	133	2,850	133
Change in Unrealized Incl in OCI	48		73
Liabilities
Balance at Beginning of Period	2,957		0	118
F&G Acquisition			2,857
Liabilities, Total Gains (Losses) Included in Earnings	209		309
Liabilities, Total Gains (Losses) Included in AOCI	0		0
Liabilities, Purchases	0		0
Liabilities, Sales	0		0
Liabilities, Settlements	0		0
Liabilities, Net transfer In (Out) of Level 3	0		0
Balance at End of Period	3,166		3,166
Change in Unrealized Incl in OCI	0		0
Future policy benefits
Liabilities
Balance at Beginning of Period	5		0
F&G Acquisition			5
Liabilities, Total Gains (Losses) Included in Earnings	0		0
Liabilities, Total Gains (Losses) Included in AOCI	0		0
Liabilities, Purchases	0		0
Liabilities, Sales	0		0
Liabilities, Settlements	0		0
Liabilities, Net transfer In (Out) of Level 3	0		0
Balance at End of Period	5		5
Change in Unrealized Incl in OCI	0		0
FIA embedded derivatives, included in contractholder funds
Liabilities
Balance at Beginning of Period	2,952		0
F&G Acquisition			2,852
Liabilities, Total Gains (Losses) Included in Earnings	209		309
Liabilities, Total Gains (Losses) Included in AOCI	0		0
Liabilities, Purchases	0		0
Liabilities, Sales	0		0
Liabilities, Settlements	0		0
Liabilities, Net transfer In (Out) of Level 3	0		0
Balance at End of Period	3,161		3,161
Change in Unrealized Incl in OCI	0		0
Asset-backed securities
Fixed maturity securities available-for-sale:
Balance at Beginning of Period	1,016		0
F&G Acquisition			854
Assets, Total Gains (Losses) Included in Earnings	(1)		(1)
Assets, Total Gains (Losses) Included in AOCI	11		20
Assets, Purchases	118		209
Assets, Sales	1		(1)
Assets, Settlements	(109)		(114)
Assets, Net transfer In (Out) of Level 3	(90)		(23)
Balance at End of Period	944		944
Change in Unrealized Incl in OCI	12		21
Commercial mortgage-backed securities
Fixed maturity securities available-for-sale:
Balance at Beginning of Period	26		0
F&G Acquisition			26
Assets, Total Gains (Losses) Included in Earnings	0		0
Assets, Total Gains (Losses) Included in AOCI	0		0
Assets, Purchases	0		0
Assets, Sales	0		0
Assets, Settlements	0		0
Assets, Net transfer In (Out) of Level 3	0		0
Balance at End of Period	26		26
Change in Unrealized Incl in OCI	1		1
Corporates
Fixed maturity securities available-for-sale:
Balance at Beginning of Period	1,264	16	17	17
F&G Acquisition			1,238
Assets, Total Gains (Losses) Included in Earnings	(1)	0	(4)	1
Assets, Total Gains (Losses) Included in AOCI	21	0	47	(1)
Assets, Purchases	3	1	3	6
Assets, Sales	0	0	0	(1)
Assets, Settlements	(20)	0	(34)	0
Assets, Net transfer In (Out) of Level 3	0	0	0	(5)
Balance at End of Period	1,267	17	1,267	17
Change in Unrealized Incl in OCI	19		45
Hybrids
Fixed maturity securities available-for-sale:
Balance at Beginning of Period	4		0
F&G Acquisition			4
Assets, Total Gains (Losses) Included in Earnings	0		0
Assets, Total Gains (Losses) Included in AOCI	0		0
Assets, Purchases	0		0
Assets, Sales	0		0
Assets, Settlements	0		0
Assets, Net transfer In (Out) of Level 3	0		0
Balance at End of Period	4		4
Change in Unrealized Incl in OCI	0		0
Municipals
Fixed maturity securities available-for-sale:
Balance at Beginning of Period	40		0
F&G Acquisition			38
Assets, Total Gains (Losses) Included in Earnings	0		0
Assets, Total Gains (Losses) Included in AOCI	2		4
Assets, Purchases	0		0
Assets, Sales	0		0
Assets, Settlements	0		0
Assets, Net transfer In (Out) of Level 3	0		0
Balance at End of Period	42		42
Change in Unrealized Incl in OCI	2		5
Residential mortgage-backed securities
Fixed maturity securities available-for-sale:
Balance at Beginning of Period	509		0
F&G Acquisition			534
Assets, Total Gains (Losses) Included in Earnings	0		0
Assets, Total Gains (Losses) Included in AOCI	12		(3)
Assets, Purchases	5		6
Assets, Sales	0		0
Assets, Settlements	(25)		(29)
Assets, Net transfer In (Out) of Level 3	0		(7)
Balance at End of Period	501		501
Change in Unrealized Incl in OCI	14		1
Foreign Governments
Fixed maturity securities available-for-sale:
Balance at Beginning of Period	16		0
F&G Acquisition			16
Assets, Total Gains (Losses) Included in Earnings	0		0
Assets, Total Gains (Losses) Included in AOCI	0		0
Assets, Purchases	0		0
Assets, Sales	0		0
Assets, Settlements	0		0
Assets, Net transfer In (Out) of Level 3	0		0
Balance at End of Period	16		16
Change in Unrealized Incl in OCI	0		0
Equity securities
Fixed maturity securities available-for-sale:
Balance at Beginning of Period	1		1
F&G Acquisition			1
Assets, Total Gains (Losses) Included in Earnings	1		0
Assets, Total Gains (Losses) Included in AOCI	0		0
Assets, Purchases	2		2
Assets, Sales	0		0
Assets, Settlements	0		0
Assets, Net transfer In (Out) of Level 3	0		0
Balance at End of Period	4		4
Change in Unrealized Incl in OCI	0		0
Available-for-sale embedded derivative
Fixed maturity securities available-for-sale:
Balance at Beginning of Period	21		0
F&G Acquisition			20
Assets, Total Gains (Losses) Included in Earnings	2		3
Assets, Total Gains (Losses) Included in AOCI	0		0
Assets, Purchases	0		0
Assets, Sales	0		0
Assets, Settlements	0		0
Assets, Net transfer In (Out) of Level 3	0		0
Balance at End of Period	23		23
Change in Unrealized Incl in OCI	0		0
Credit linked note
Fixed maturity securities available-for-sale:
Balance at Beginning of Period	23		0
F&G Acquisition			23
Assets, Total Gains (Losses) Included in Earnings	0		0
Assets, Total Gains (Losses) Included in AOCI	0		0
Assets, Purchases	0		0
Assets, Sales	0		0
Assets, Settlements	0		0
Assets, Net transfer In (Out) of Level 3	0		0
Balance at End of Period	23		23
Change in Unrealized Incl in OCI	0		0
Other long-term investments
Fixed maturity securities available-for-sale:
Balance at Beginning of Period		112	120	101
F&G Acquisition			0
Assets, Total Gains (Losses) Included in Earnings		4	(61)	15
Assets, Total Gains (Losses) Included in AOCI		0	0	0
Assets, Purchases		0	0	0
Assets, Sales		0	0	0
Assets, Settlements		0	0	0
Assets, Net transfer In (Out) of Level 3		0	(59)	0
Balance at End of Period	$ 0	$ 116	0	$ 116
Change in Unrealized Incl in OCI			$ 0

Fair Value, Measurement With Unobservable Inputs Reconciliation, Recurring Basis, Asset, Business Combinations

No definition available.

Name:	fnf_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetBusinessCombinations
Namespace Prefix:	fnf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Fair Value, Measurement With Unobservable Inputs Reconciliation, Recurring Basis, Business Combinations

+ References

No definition available.

+ Details

Name:	fnf_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisBusinessCombinations
Namespace Prefix:	fnf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Unrealized Gain (Loss) Included in Other Comprehensive Income (Loss)

+ References

No definition available.

+ Details

Name:	fnf_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityUnrealizedGainLossIncludedInOtherComprehensiveIncomeLoss
Namespace Prefix:	fnf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of unrealized gain (loss) recognized in other comprehensive income (OCI) from asset measured at fair value on recurring basis using unobservable input (level 3) and still held.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossOci
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of gain (loss) recognized in other comprehensive income (OCI) from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of transfer of financial instrument classified as an asset into (out of) level 3 of the fair value hierarchy.

+ References

No definition available.

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

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

- Definition

Amount of gain (loss) recognized in income from liability measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of gain (loss) recognized in other comprehensive income (OCI) from liability measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of purchases of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of sales of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySales
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of transfers of financial instrument classified as a liability into (out of) level 3 of the fair value hierarchy.

+ References

No definition available.

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_LiabilitiesFairValueDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=fnf_FuturePolicyBenefitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=fnf_EmbeddedDerivativesIncludedInContractholderFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=fnf_HybridsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ResidentialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=fnf_AvailableForSaleEmbeddedDerivativesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_BankLoanObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_OtherLongTermInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: