Retirement Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 29, 2014	Mar. 30, 2013
Pension Benefits
Net periodic benefit cost
Service cost	$ 27	$ 33
Interest cost	79	73
Expected return on plan assets	(111)	(105)
Amortization of prior service cost (credit)	4	4
Amortization of net actuarial loss	28	46
Net periodic benefit cost	27	51
Postretirement Benefits Other than Pensions
Net periodic benefit cost
Service cost	1	2
Interest cost	5	5
Amortization of prior service cost (credit)	(6)	(3)
Amortization of net actuarial loss	1	2
Net periodic benefit cost	$ 1	$ 6