Pensions and Other Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Apr. 01, 2018
Retirement Plans
Components of net periodic benefit cost
Service cost	$ 276	$ 309
Interest cost	275	252
Expected return on plan assets	(583)	(560)
Amortization of prior service cost/(credit)	1	1
Recognized actuarial losses	144	215
Curtailments and settlements	(1)	(2)
Net periodic benefit cost	112	215
Other Benefit Plans
Components of net periodic benefit cost
Service cost	68	67
Interest cost	46	37
Expected return on plan assets	(2)	(2)
Amortization of prior service cost/(credit)	(8)	(8)
Recognized actuarial losses	32	30
Curtailments and settlements	0	0
Net periodic benefit cost	$ 136	$ 124