Fair Value Measurements (Pension Plan Assets) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 26, 2014	Dec. 27, 2013
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	$ 2,504	$ 2,500
Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Investment Committee equity target allocation percentage of pension assets	70.00%
Pension plan assets at fair value	1,715	1,619
Information technology [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	177	173
Health care [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	133	126
Consumer discretionary [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	125	152
Financials [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	116	116
Industrials [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	90	108
Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	51	59
Consumer staples [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	42	43
Materials [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	20	29
Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	33	31
Fixed Income Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Investment Committee equity target allocation percentage of pension assets	30.00%
Pension plan assets at fair value	740	795
Mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	20	17
Cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	1	0
Common trust funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	611	553
Corporate bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	539	568
Partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	365	314
Government securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	164	186
Asset-backed securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	15	24
Derivatives and other [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	2	1
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	808	854
Level 1 [Member] | Information technology [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	177	173
Level 1 [Member] | Health care [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	133	126
Level 1 [Member] | Consumer discretionary [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	125	152
Level 1 [Member] | Financials [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	116	116
Level 1 [Member] | Industrials [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	90	108
Level 1 [Member] | Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	51	59
Level 1 [Member] | Consumer staples [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	42	43
Level 1 [Member] | Materials [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	20	29
Level 1 [Member] | Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	33	31
Level 1 [Member] | Mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	20	17
Level 1 [Member] | Cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	1	0
Level 1 [Member] | Common trust funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 1 [Member] | Corporate bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 1 [Member] | Partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 1 [Member] | Government securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 1 [Member] | Asset-backed securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 1 [Member] | Derivatives and other [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	1,696	1,646
Level 2 [Member] | Information technology [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 [Member] | Health care [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 [Member] | Consumer discretionary [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 [Member] | Financials [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 [Member] | Industrials [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 [Member] | Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 [Member] | Consumer staples [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 [Member] | Materials [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 [Member] | Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 [Member] | Mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 [Member] | Cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 [Member] | Common trust funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	611	553
Level 2 [Member] | Corporate bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	539	568
Level 2 [Member] | Partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	365	314
Level 2 [Member] | Government securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	164	186
Level 2 [Member] | Asset-backed securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	15	24
Level 2 [Member] | Derivatives and other [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	2	1
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | Information technology [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | Health care [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | Consumer discretionary [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | Financials [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | Industrials [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | Consumer staples [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | Materials [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | Mutual funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | Cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | Common trust funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | Corporate bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | Partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | Government securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | Asset-backed securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 3 [Member] | Derivatives and other [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	$ 0	$ 0