Derivative Financial Instruments - Narrative (Details) $ in Millions	9 Months Ended
Sep. 30, 2021 USD ($) contract	Dec. 31, 2020 USD ($) contract
Embedded derivatives
Derivative [Line Items]
Term of contract, term one	1 year
Term of contract, term two	2 years
Term of contract, term three	3 years
Term of contract, term four	5 years
Call options \| Not Designated as Hedging Instrument
Derivative [Line Items]
Collateral posted	$ 582	$ 491
Maximum amount of loss due to credit risk	40	58
Call options \| Derivatives for Trading and Investment \| Not Designated as Hedging Instrument
Derivative [Line Items]
Collateral posted	582	491
Maximum amount of loss due to credit risk	40	58
Call options \| Cash and Cash Equivalents \| Not Designated as Hedging Instrument
Derivative [Line Items]
Collateral posted	$ 429	$ 415
Futures contracts
Derivative [Line Items]
Number of instruments held \| contract	354,000,000	384,000,000
Collateral held	$ 3	$ 4

Derivative, Term of Contract, Term Four

No definition available.

Name:	fnf_DerivativeTermofContractTermFour
Namespace Prefix:	fnf_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Derivative, Term of Contract, Term One

+ References

No definition available.

+ Details

Name:	fnf_DerivativeTermofContractTermOne
Namespace Prefix:	fnf_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Derivative, Term of Contract, Term Three

+ References

No definition available.

+ Details

Name:	fnf_DerivativeTermofContractTermThree
Namespace Prefix:	fnf_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Derivative, Term of Contract, Term Two

+ References

No definition available.

+ Details

Name:	fnf_DerivativeTermofContractTermTwo
Namespace Prefix:	fnf_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5624258-113959

+ Details

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

- Definition

Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=117331979&loc=d3e41228-113958

+ Details

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

- Definition

Fair value, after effects of master netting arrangements, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset offset against an obligation to return collateral. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=d3e41678-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226016-175313

+ Details

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

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

- Definition

The number of derivative instruments of a particular group held by the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5580258-113959

+ Details

Name:	us-gaap_DerivativeNumberOfInstrumentsHeld
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_EmbeddedDerivativeFinancialInstrumentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_CallOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=fnf_DerivativesForTradingAndInvestmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_CashAndCashEquivalentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_FutureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: