Contractholder Funds - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2026	Dec. 31, 2025
Insurance [Abstract]
Change in total benefits and other changes in policy reserves (decrease) increase	$ (5)	$ (22)

Policyholder Benefits And Claims Incurred, Net, Life and Annuity, Change In Policy Reserves, Increase (Decrease)

No definition available.

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