Employee Benefit Plans (Components of Net Periodic Benefit Cost (Credit) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 4
Interest cost	6	8
Expected return on assets	(11)	(10)
Amortization of actuarial losses	2	4
Net periodic benefit cost	0	6
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1
Interest cost	2	2
Expected return on assets	0	0
Amortization of actuarial losses	0	0
Net periodic benefit cost	$ 3	$ 3