Retirement Plans - Net periodic benefit cost (credit) and other changes in plan assets and benefit obligations recognized in OCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Other changes in plan assets and benefit obligations recognized in OCI
Current year actuarial loss (gain)	$ 248	$ (18)	$ 382
Amortization of net actuarial gain (loss)	(152)	(136)	(104)
Amortization of prior service credit (cost)	(9)	(7)	7
Pension Benefits
Net periodic benefit cost
Service cost	104	100	98
Interest cost	306	323	338
Expected return on plan assets	(553)	(507)	(490)
Amortization of prior service cost (credit)	15	15	15
Amortization of net actuarial loss	153	137	104
Net periodic benefit cost	25	68	65
Other changes in plan assets and benefit obligations recognized in OCI
Current year actuarial loss (gain)	270	(11)	399
Current year prior service cost (credit)	20	1
Amortization of net actuarial gain (loss)	(153)	(137)	(104)
Amortization of prior service credit (cost)	(15)	(15)	(15)
Business disposition	(7)
Total recognized in OCI, before taxes	115	(162)	280
Total recognized in net periodic benefit cost (credit) and OCI	140	(94)	345
Postretirement Benefits Other Than Pensions
Net periodic benefit cost
Service cost	3	3	3
Interest cost	10	12	16
Amortization of prior service cost (credit)	(6)	(8)	(22)
Amortization of net actuarial loss	(1)	(1)
Net periodic benefit cost	6	6	(3)
Other changes in plan assets and benefit obligations recognized in OCI
Current year actuarial loss (gain)	(22)	(7)	(17)
Current year prior service cost (credit)			(12)
Amortization of net actuarial gain (loss)	1	1
Amortization of prior service credit (cost)	6	8	22
Total recognized in OCI, before taxes	(15)	2	(7)
Total recognized in net periodic benefit cost (credit) and OCI	$ (9)	$ 8	$ (10)