Retirement Plans - Components of Net Periodic Pension Cost (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Retirement Benefits [Abstract]
Service cost	$ 14	$ 11	$ 28	$ 21
Interest cost	19	24	37	48
Expected return on plan assets	(45)	(45)	(90)	(90)
Amortization of unrecognized net actuarial losses	12	12	24	23
Pension (income) expense	0	2	(1)	2
Net non-service pension (income) costs included in Other, net	$ (14)	$ (9)	$ (29)	$ (19)