Revenue - Disaggregated Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 1,016	$ 1,112	$ 2,067	$ 2,270
Point in time
Disaggregation of Revenue [Line Items]
Revenue	32	34	62	73
Over time
Disaggregation of Revenue [Line Items]
Revenue	984	1,078	2,005	2,197
Commercial Industries
Disaggregation of Revenue [Line Items]
Revenue	520	592	1,092	1,204
Commercial Industries | Customer Experience Management
Disaggregation of Revenue [Line Items]
Revenue	157	158	325	329
Commercial Industries | Business Operations Solutions
Disaggregation of Revenue [Line Items]
Revenue	133	157	286	323
Commercial Industries | Commercial Healthcare Solutions
Disaggregation of Revenue [Line Items]
Revenue	103	123	216	245
Commercial Industries | Human Resource Services
Disaggregation of Revenue [Line Items]
Revenue	127	154	265	307
Government services
Disaggregation of Revenue [Line Items]
Revenue	331	326	621	651
Government services | Government Healthcare Solutions
Disaggregation of Revenue [Line Items]
Revenue	154	175	306	352
Government services | Government Services Solutions
Disaggregation of Revenue [Line Items]
Revenue	177	151	315	299
Transportation Services
Disaggregation of Revenue [Line Items]
Revenue	165	194	354	378
Transportation Services | Roadway Charging & Management Services
Disaggregation of Revenue [Line Items]
Revenue	71	81	149	160
Transportation Services | Transit Solutions
Disaggregation of Revenue [Line Items]
Revenue	61	62	128	116
Transportation Services | Curbside Management Solutions
Disaggregation of Revenue [Line Items]
Revenue	14	28	36	55
Transportation Services | Public Safety Solutions
Disaggregation of Revenue [Line Items]
Revenue	17	20	37	41
Transportation Services | Commercial Vehicles
Disaggregation of Revenue [Line Items]
Revenue	2	3	4	6
Other
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	37
Other | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	36
Other | Education
Disaggregation of Revenue [Line Items]
Revenue	$ 0	$ 0	$ 0	$ 1