Contingencies and Litigation - Litigation Against the Company (Details) $ in Millions	1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended	18 Months Ended	21 Months Ended
	Feb. 28, 2019 USD ($)	Mar. 31, 2018 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2018 USD ($) claim	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2017 USD ($)
Surety Bond
Loss Contingencies [Line Items]
Maximum exposure, undiscounted			$ 564		$ 564	$ 564
Letters of Credit Issued to Secured Contractual Obligations
Loss Contingencies [Line Items]
Maximum exposure, undiscounted			229		229	229
State Of Texas v. Xerox Corporation, Xerox State Healthcare, LLC, and ACS State Healthcare, LLC | Settled Litigation
Loss Contingencies [Line Items]
Loss contingencies, settlement amount	$ 236
Loss contingency, damages paid			118
Loss contingency, damages to be paid			$ 118
Conduent Business Services, LLC v. Cognizant Business Service, LLC | Pending Litigation
Loss Contingencies [Line Items]
Loss contingency, damages sought		$ 47				$ 90
Gain contingency, damages sought							$ 150
Number of counterclaims for breach of contract | claim				2
Loss contingency, damages sought, termination fees				$ 25
Loss contingency, additional damages sought					$ 43