Retirement Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 28, 2014	Jun. 29, 2013	Jun. 28, 2014	Jun. 29, 2013
Pension Benefits
Net periodic benefit cost
Service cost	$ 27	$ 34	$ 54	$ 67
Interest cost	85	73	164	146
Expected return on plan assets	(117)	(105)	(228)	(210)
Amortization of prior service cost (credit)	4	3	8	7
Amortization of net actuarial loss	28	46	56	92
Net periodic benefit cost	27	51	54	102
Postretirement Benefits Other than Pensions
Net periodic benefit cost
Service cost	1	2	2	4
Interest cost	5	5	10	10
Amortization of prior service cost (credit)	(5)	(2)	(11)	(5)
Amortization of net actuarial loss		1	1	3
Net periodic benefit cost	$ 1	$ 6	$ 2	$ 12