Retirement Plans (Details) - USD ($) $ in Millions		3 Months Ended
	Jan. 01, 2019	Mar. 31, 2019	Apr. 01, 2018
Defined Benefit Plan Disclosure [Line Items]
Decrease in expected long-term returns on assets	1.00%
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 28	$ 46
Interest cost		150	114
Expected return on plan assets		(228)	(179)
Recognized net actuarial loss (gain)		70	96
Amortization of prior service credit		(4)	(11)
Net periodic benefit cost (credit)		16	66
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost		2	3
Interest cost		9	8
Expected return on plan assets		(9)	(9)
Recognized net actuarial loss (gain)		(2)	(1)
Amortization of prior service credit		(1)	(1)
Net periodic benefit cost (credit)		$ (1)	$ 0