Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 29, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 29, 2018	Dec. 30, 2017
Disaggregation of Revenue [Line Items]
Net sales	$ 1,008	$ 1,018	$ 1,009	$ 941	$ 903	$ 923	$ 1,005	$ 947	$ 3,976	$ 3,778	$ 3,580
Net Agency Revenue
Disaggregation of Revenue [Line Items]
Net sales									18	26	16
Gross billings from Net Agency Revenue									447	454	402
North America
Disaggregation of Revenue [Line Items]
Net sales									2,111	1,939	1,876
Europe
Disaggregation of Revenue [Line Items]
Net sales									1,509	1,463	1,373
APAC & Emerging Markets
Disaggregation of Revenue [Line Items]
Net sales									368	387	349
Operating Segments | North America
Disaggregation of Revenue [Line Items]
Net sales									2,111	1,939	1,876
Operating Segments | Europe
Disaggregation of Revenue [Line Items]
Net sales									1,509	1,463	1,373
Operating Segments | APAC & Emerging Markets
Disaggregation of Revenue [Line Items]
Net sales									368	387	349
Operating Segments | Supply Chain Services
Disaggregation of Revenue [Line Items]
Net sales									3,678	3,689	3,478
Operating Segments | Supply Chain Services | North America
Disaggregation of Revenue [Line Items]
Net sales									1,816	1,858	1,795
Operating Segments | Supply Chain Services | Europe
Disaggregation of Revenue [Line Items]
Net sales									1,513	1,462	1,359
Operating Segments | Supply Chain Services | APAC & Emerging Markets
Disaggregation of Revenue [Line Items]
Net sales									361	380	342
Operating Segments | Software Solutions
Disaggregation of Revenue [Line Items]
Net sales									99	101	101
Operating Segments | Software Solutions | North America
Disaggregation of Revenue [Line Items]
Net sales									82	83	83
Operating Segments | Software Solutions | Europe
Disaggregation of Revenue [Line Items]
Net sales									10	11	11
Operating Segments | Software Solutions | APAC & Emerging Markets
Disaggregation of Revenue [Line Items]
Net sales									7	7	7
Operating Segments | Prescription Management
Disaggregation of Revenue [Line Items]
Net sales									246	0	0
Operating Segments | Prescription Management | North America
Disaggregation of Revenue [Line Items]
Net sales									246	0	0
Operating Segments | Prescription Management | Europe
Disaggregation of Revenue [Line Items]
Net sales									0	0	0
Operating Segments | Prescription Management | APAC & Emerging Markets
Disaggregation of Revenue [Line Items]
Net sales									0	0	0
Eliminations
Disaggregation of Revenue [Line Items]
Net sales									(47)	(12)	1
Eliminations | North America
Disaggregation of Revenue [Line Items]
Net sales									(33)	(2)	(2)
Eliminations | Europe
Disaggregation of Revenue [Line Items]
Net sales									(14)	(10)	3
Eliminations | APAC & Emerging Markets
Disaggregation of Revenue [Line Items]
Net sales									0	0	0
Eliminations
Disaggregation of Revenue [Line Items]
Net sales									(12)	(11)	(18)
Eliminations | Supply Chain Services
Disaggregation of Revenue [Line Items]
Net sales									(12)	(11)	(18)
Eliminations | Software Solutions
Disaggregation of Revenue [Line Items]
Net sales									0	0	0
Eliminations | Prescription Management
Disaggregation of Revenue [Line Items]
Net sales									$ 0	$ 0	$ 0