Employee Benefits - Fair Values For Other Postretirement Benefit Plans By Asset Category (Detail) - Health Care and Life - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	$ 450	$ 581	$ 572
Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	441	568
Fair Value, Inputs, Level 1, 2 and 3 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	30	36
Fair Value, Inputs, Level 1, 2 and 3 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	252	284
Fair Value, Inputs, Level 1, 2 and 3 | U.S. Treasuries and agencies
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	101	160
Fair Value, Inputs, Level 1, 2 and 3 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	35	64
Fair Value, Inputs, Level 1, 2 and 3 | International bonds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	12	14
Fair Value, Inputs, Level 1, 2 and 3 | Other
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	11	10
Level 1
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	369	494
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	1	0
Level 1 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	252	284
Level 1 | U.S. Treasuries and agencies
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	82	150
Level 1 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	25	50
Level 1 | International bonds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	9	10
Level 1 | Other
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	0	0
Level 2
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	72	74
Level 2 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	29	36
Level 2 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	0	0
Level 2 | U.S. Treasuries and agencies
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	19	10
Level 2 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	10	14
Level 2 | International bonds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	3	4
Level 2 | Other
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	11	10
Level 3
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	0	0
Level 3 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	0	0
Level 3 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	0	0
Level 3 | U.S. Treasuries and agencies
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	0	0
Level 3 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	0	0
Level 3 | International bonds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	0	0
Level 3 | Other
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	0	0
Investments measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, plan assets amount	$ 9	$ 13