Pension And Other Retirement Benefits - Components of Net Periodic Benefit Expense Related to Retirement Plans (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 19	$ 22	$ 19
U.S. Plans | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	17	17	19
Interest cost	17	21	17
Expected return on plan assets	(20)	(20)	(15)
Amortization of net actuarial loss and prior service credits from earlier periods	7	4	6
Net periodic expense	21	22	27
U.S. Plans | Other Retirement Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	3	3	3
Interest cost	1	1	1
Expected return on plan assets	0	0	0
Amortization of net actuarial loss and prior service credits from earlier periods	0	0	0
Net periodic expense	$ 4	$ 4	$ 4