Intangible Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Accelerated amortization expense	$ 18	$ 53

Restructuring And Related Cost, Accelerated Amortization

No definition available.

Name:	fisv_RestructuringAndRelatedCostAcceleratedAmortization
Namespace Prefix:	fisv_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration