Retirement Plans - Components of Net Periodic Pension Cost (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Retirement Benefits [Abstract]
Service cost	$ 13	$ 14	$ 27	$ 28
Interest cost	14	19	28	37
Expected return on plan assets	(49)	(45)	(99)	(90)
Amortization of unrecognized net actuarial losses	13	12	28	24
Settlement loss	3	0	4	0
Pension (income) expense	(6)	0	(12)	(1)
Net non-service pension (income) costs included in other, net	$ (19)	$ (14)	$ (39)	$ (29)