Employee Benefit Plans (Components of Net Periodic Benefit Cost) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 15	$ 17	$ 18
Interest cost	28	29	32
Expected return on assets	(40)	(48)	(46)
Prior service cost amortization	0	0	1
Amortization of actuarial losses	11	11	14
Settlement loss	16	0	0
Curtailment	6	0	0
Net periodic benefit cost	36	9	19
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	3	4	4
Interest cost	9	8	9
Amortization of actuarial losses	0	0	1
Curtailment	3	0	0
Net periodic benefit cost	$ 15	$ 12	$ 14