Pensions and Other Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Retirement Plans
Components of net periodic benefit cost
Service cost	$ 307	$ 266	$ 925	$ 772
Interest cost	247	232	748	693
Expected return on plan assets	(550)	(514)	(1,664)	(1,528)
Amortization of prior service cost/(credit)	1	1	2	2
Recognized actuarial losses	213	154	641	456
Curtailments and settlements	0	2	(2)	1
Net periodic benefit cost	218	141	650	396
Other Benefit Plans
Components of net periodic benefit cost
Service cost	67	62	202	185
Interest cost	37	40	112	119
Expected return on plan assets	(1)	(2)	(5)	(5)
Amortization of prior service cost/(credit)	(7)	(8)	(23)	(23)
Recognized actuarial losses	31	34	92	103
Curtailments and settlements	0	0	0	0
Net periodic benefit cost	$ 127	$ 126	$ 378	$ 379