Financial Instruments (Narrative) (Details) - Level 1 - USD ($) $ in Millions	Sep. 24, 2016	Dec. 26, 2015
Money Market Funds
Schedule of Investments [Line Items]
Available-for-sale investments used as collateral	$ 3	$ 1
Mutual Funds
Schedule of Investments [Line Items]
Restricted investments	$ 14	$ 15

The fair value of available-for-sale securities that serve as collateral for borrowings.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5086-111524

Name:	us-gaap_AvailableForSaleSecuritiesPledgedAsCollateral
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant