Employee Benefits - Narrative (Detail)	1 Months Ended	12 Months Ended
	Jul. 31, 2022	Dec. 31, 2022 USD ($) plan shares	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation for all defined benefit pension plans		$ 15,300,000,000	$ 20,100,000,000
Pension and benefit credits from assumptions used calculating benefit obligation, discount rate		$ 7,000,000,000	$ 1,100,000,000	$ 3,200,000,000
Discount rate		5.20%	2.90%	2.60%	3.30%
Extension term	3 years
Defined benefit plan, reclassification adjustment from AOCI		$ 390,000,000	$ 708,000,000	$ 708,000,000
Defined benefit plan, period used to determine overall expected long term rate of return on assets assumption (in years)		10 years
Number of leveraged employee stock ownership plans (ESOP) | plan		4
Number of allocated shares of common stock in ESOP (in shares) | shares		43,000,000
Number of unallocated shares of common stock in ESOP (in shares) | shares		0
Total savings plan cost		$ 620,000,000	690,000,000	730,000,000
Net pre-tax pension and benefits credits		1,700,000,000	2,400,000,000	1,600,000,000
Pension and benefit (charge) credits from actual return		(5,500,000,000)	847,000,000	(1,600,000,000)
Pension and benefit credits from actuarial assumption adjustments		206,000,000	453,000,000
Charged to expense		319,000,000	$ 233,000,000	309,000,000
Minimum
Defined Benefit Plan Disclosure [Line Items]
Selected bonds		$ 300,000,000
Return Seeking Assets | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage of assets		41.00%
Return Seeking Assets | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage of assets		51.00%
Liability Hedging Assets | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage of assets		55.00%
Liability Hedging Assets | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage of assets		65.00%
Cash and cash equivalents | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation percentage of assets		10.00%
Pension
Defined Benefit Plan Disclosure [Line Items]
Pension and benefit credits from assumptions used calculating benefit obligation, discount rate		$ 4,100,000,000
Discount rate		5.20%	3.00%
Plan amendments		$ 427,000,000	$ 0
Change in defined benefit and postretirement plans, due to change in prior service credit, net of taxes		317,000,000
Change in defined benefit and postretirement plans, due to change in prior service credit, tax		110,000,000
Defined benefit plan contributions by employer		53,000,000	56,000,000
Defined benefit plan contributions by employer in next fiscal year		200,000,000
Net pre-tax pension and benefits credits		(1,505,000,000)	$ 1,419,000,000	(744,000,000)
Pension | Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan contributions by employer		0
Pension | Nonqualified Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan contributions by employer		53,000,000
Health Care and Life
Defined Benefit Plan Disclosure [Line Items]
Pension and benefit credits from assumptions used calculating benefit obligation, discount rate		$ 2,900,000,000
Discount rate		5.20%	2.90%
Plan amendments		$ 4,000,000	$ 0
Defined benefit plan contributions by employer		692,000,000	885,000,000
Defined benefit plan contributions by employer in next fiscal year		820,000,000
Net pre-tax pension and benefits credits		$ 3,182,000,000	$ 960,000,000	$ (866,000,000)
Pension and Postretirement Plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate		5.20%