Receivables (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 30, 2019	Mar. 31, 2018
Receivables [Abstract]
Client cash collections	$ 1,360	$ 1,270

Cash receipts from customers during the current period which are usually for sales of goods and services.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3536-108585

Name:	us-gaap_ProceedsFromCustomers
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration