Employee Benefit Plans (Net Periodic Benefit Cost (Credit)) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 36	$ 42
Interest cost	83	79
Expected return on plan assets	(223)	(208)
Amortization of net actuarial loss	40	48
Settlements		(2)
Net periodic benefit (credit) cost	(64)	(41)
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	6
Interest cost	11	12
Expected return on plan assets	(48)	(44)
Amortization of prior service (credit) cost	(10)	(10)
Amortization of net actuarial loss		1
Net periodic benefit (credit) cost	$ (41)	$ (35)