Revenue from Contracts with Customers (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)
Revenue from Contract with Customer [Abstract]
Contract with Customer, Liability, Revenue Recognized		$ 287
Capitalized Contract Cost, Net	$ 85	85
Capitalized Contract Cost, Amortization	$ 10	$ 18
Revenue, Judgment		Our contracts with clients typically include various combinations of our software solutions and related services. Determining whether such software solutions and services are considered distinct performance obligations that should be accounted for separately versus together may require significant judgment. Specifically, judgment is required to determine whether software licenses are distinct from services and hosting included in an arrangement
Revenue, Information Used to Allocate Transaction Price		Contract transaction price is allocated to performance obligations using estimated stand-alone selling price
Revenue, Information Used to Determine Transaction Price		We determine stand-alone selling price maximizing observable inputs such as stand-alone sales when they exist or substantive renewal prices charged to clients. In instances where stand-alone selling price is not observable, we utilize an estimate of stand-alone selling price. Such estimates are derived from various methods that include: cost plus margin, historical pricing practices, and the residual approach, which requires a considerable amount of judgment
Revenue, Practical Expedient, Initial Application and Transition, Nonrestatement of Modified Contract [true/false]		true