Employee Benefit Plans (Net Periodic Benefit Cost (Credit)) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 24	$ 35	$ 72	$ 106
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)
Interest cost	$ 111	$ 83	$ 332	$ 250
Expected return on plan assets	(216)	(221)	(648)	(667)
Amortization of net actuarial (gain) loss		39		119
Net periodic benefit (credit) cost	(81)	(64)	(244)	(192)
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 5	$ 10	$ 16
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)
Interest cost	$ 15	$ 11	$ 46	$ 34
Expected return on plan assets	(37)	(47)	(113)	(143)
Amortization of prior service cost (credit)	(10)	(10)	(28)	(29)
Amortization of net actuarial (gain) loss	(1)		(4)	(1)
Settlements and curtailment		(8)		(8)
Net periodic benefit (credit) cost	$ (30)	$ (49)	$ (89)	$ (131)