Retirement Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 01, 2017	Jul. 02, 2016	Jul. 01, 2017	Jul. 02, 2016
Pension Benefits
Net periodic benefit cost (credit)
Service cost	$ 25	$ 25	$ 50	$ 49
Interest cost	81	85	161	170
Expected return on plan assets	(127)	(122)	(253)	(245)
Amortization of net actuarial loss	34	26	68	52
Amortization of prior service cost (credit)	4	3	8	7
Net periodic benefit cost (credit)	17	17	34	33
Postretirement Benefits Other Than Pensions
Net periodic benefit cost (credit)
Service cost			1	1
Interest cost	3	4	6	8
Amortization of prior service cost (credit)	(2)	(5)	(4)	(11)
Net periodic benefit cost (credit)	$ 1	$ (1)	$ 3	$ (2)