Retirement Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 28, 2013	Sep. 29, 2012	Sep. 28, 2013	Sep. 29, 2012	Dec. 29, 2012
Plan amendment adjustment
Amendment to postretirement benefit plan, pre-tax	$ 55		$ 55
Pension Benefits
Net periodic benefit cost
Service cost	33	30	100	89
Interest cost	72	77	218	229
Expected return on plan assets	(104)	(102)	(314)	(305)
Amortization of prior service cost (credit)	4	4	11	12
Amortization of net actuarial loss	46	29	138	88
Net periodic benefit cost	51	38	153	113
Postretirement Benefits Other than Pensions
Net periodic benefit cost
Service cost	1	2	5	5
Interest cost	5	6	15	19
Amortization of prior service cost (credit)	(6)	(3)	(11)	(9)
Amortization of net actuarial loss	2	2	5	5
Net periodic benefit cost	2	7	14	20
Discount rate as a percent	4.50%		4.50%		3.75%
Plan amendment adjustment
Amendment to postretirement benefit plan, pre-tax	$ 55		$ 55