Retirement Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 03, 2020	Sep. 28, 2019	Oct. 03, 2020	Sep. 28, 2019
Pension Benefits
Net periodic benefit cost (credit)
Service cost	$ 27	$ 23	$ 79	$ 68
Interest cost	73	82	220	245
Expected return on plan assets	(144)	(139)	(431)	(417)
Amortization of net actuarial loss	47	26	139	76
Amortization of prior service cost	3	3	9	10
Net periodic benefit cost (credit)	6	(5)	16	(18)
Postretirement Benefits Other Than Pensions
Net periodic benefit cost (credit)
Service cost	0	1	2	2
Interest cost	2	3	6	8
Amortization of net actuarial loss	(1)	(1)	(1)	(2)
Amortization of prior service cost	(1)	(2)	(4)	(5)
Net periodic benefit cost (credit)	$ 0	$ 1	$ 3	$ 3