Pensions and Other Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 29, 2020	Mar. 31, 2019
Retirement Plans
Components of net periodic benefit cost
Service cost	$ 326	$ 276
Interest cost	240	275
Expected return on plan assets	(614)	(583)
Amortization of prior service cost/(credit)	0	1
Recognized actuarial losses	223	144
Curtailments and settlements	19	(1)
Net periodic benefit cost	194	112
Other Benefit Plans
Components of net periodic benefit cost
Service cost	72	68
Interest cost	33	46
Expected return on plan assets	(2)	(2)
Amortization of prior service cost/(credit)	(8)	(8)
Recognized actuarial losses	36	32
Curtailments and settlements	0	0
Net periodic benefit cost	$ 131	$ 136