Segment Information - Schedule of Acquisition, Integration and Other Costs (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Segment Reporting Information
Acquisition and integration	$ 136	$ 88	$ 48
Incremental stock compensation directly attributable to specific programs	0	3	34
Total acquisition, integration and other costs	689	624	482
One-Time Performance-Related Awards
Segment Reporting Information
Incremental stock compensation directly attributable to specific programs	33	58	15
Worldpay Merchant Solutions
Segment Reporting Information
Separation of the Worldpay Merchant Solutions business	54	148	17
Enterprise Costs Control and Other Initiatives
Segment Reporting Information
Other, including divestiture-related expenses and enterprise cost control and other initiatives	62	12	20
Platform Initiatives \| Enterprise Cost Control Initiatives and Changes in Senior Management
Segment Reporting Information
Severance and other termination expenses	247	56	70
Future Forward \| Platform Modernization
Segment Reporting Information
Enterprise transformation, including Future Forward and platform modernization	$ 157	$ 262	$ 312

Corporate And Other Segment Related To Acquisition, Integration And Other Costs

No definition available.

Name:	fis_CorporateAndOtherSegmentRelatedToAcquisitionIntegrationAndOtherCosts
Namespace Prefix:	fis_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Enterprise Transformation Cost

+ References

No definition available.

+ Details

Name:	fis_EnterpriseTransformationCost
Namespace Prefix:	fis_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Other, Including Divestiture Related Expenses

+ References

No definition available.

+ Details

Name:	fis_OtherIncludingDivestitureRelatedExpenses
Namespace Prefix:	fis_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Pending Spin-off Cost

+ References

No definition available.

+ Details

Name:	fis_PendingSpinOffCost
Namespace Prefix:	fis_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section S45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479983/718-10-S45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479830/718-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

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

- Definition

Amount of expense for integration-related cost incurred in connection with business combination. Includes system integration and conversion costs; severance and other employee-related costs; restructuring and other post-combination costs. Excludes acquisition-related cost incurred to effect business combination; cost to issue debt or equity securities; and cost related to acquisition of asset.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 805
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479328/805-10-50-7

+ Details

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

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

- Definition

Amount of expenses for special or contractual termination benefits provided to current employees involuntarily terminated under a benefit arrangement associated exit or disposal activities pursuant to an authorized plan. Excludes expenses related to one-time termination benefits, a discontinued operation or an asset retirement obligation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

+ Details

Name:	us-gaap_SeveranceCosts1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_AwardTypeAxis=fis_OneTimePerformanceRelatedAwardsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=fis_WorldpayMerchantSolutionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=fis_EnterpriseCostsControlAndOtherInitiativesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CapitalizedContractCostAxis=fis_PlatformInitiativesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=fis_EnterpriseCostControlInitiativesAndChangesInSeniorManagementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_CapitalizedContractCostAxis=fis_PlatformModernizationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: