Retirement Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 29, 2013	Jun. 30, 2012	Jun. 29, 2013	Jun. 30, 2012
Pension Benefits
Net periodic benefit cost
Service cost	$ 34	$ 29	$ 67	$ 59
Interest cost	73	76	146	152
Expected return on plan assets	(105)	(102)	(210)	(203)
Amortization of prior service cost (credit)	3	4	7	8
Amortization of net actuarial loss	46	30	92	59
Net periodic benefit cost	51	37	102	75
Postretirement Benefits Other than Pensions
Net periodic benefit cost
Service cost	2	1	4	3
Interest cost	5	7	10	13
Amortization of prior service cost (credit)	(2)	(3)	(5)	(6)
Amortization of net actuarial loss	1	1	3	3
Net periodic benefit cost	$ 6	$ 6	$ 12	$ 13