Employee Benefit Plans (Fair Values of Pension and Post Retirement Plan Assets by Asset Category) (Detail) - USD ($) $ in Millions		Dec. 31, 2024	Dec. 31, 2023
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value	[1]	$ 7,840	$ 8,819
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value	[2]	2,184	2,045
Level 1 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		2,208	2,227
Level 1 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		1,375	961
Level 2 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		1,929	2,643
Level 2 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		120	147
Level 3 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		84
Level 3 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		6
Fair Value, Inputs, Level 1, 2 and 3 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		4,221	4,870
Fair Value, Inputs, Level 1, 2 and 3 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		1,501	1,108
NAV | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value	[3]	3,619	3,949
Cash equivalents and other | Level 1 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		395	21
Cash equivalents and other | Level 1 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		7	3
Cash equivalents and other | Level 2 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value			9
Cash equivalents and other | Level 2 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value			1
Cash equivalents and other | Fair Value, Inputs, Level 1, 2 and 3 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		395	30
Cash equivalents and other | Fair Value, Inputs, Level 1, 2 and 3 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		7	4
US Equity Securities | Level 1 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		1,004	1,145
US Equity Securities | Level 1 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		946	757
US Equity Securities | Fair Value, Inputs, Level 1, 2 and 3 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		1,004	1,145
US Equity Securities | Fair Value, Inputs, Level 1, 2 and 3 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		946	757
Foreign Equity Securities | Level 1 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		723	944
Foreign Equity Securities | Level 1 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		74	194
Foreign Equity Securities | Level 2 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		1	2
Foreign Equity Securities | Fair Value, Inputs, Level 1, 2 and 3 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		724	946
Foreign Equity Securities | Fair Value, Inputs, Level 1, 2 and 3 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		74	194
Insurance Contracts | Level 2 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		139	162
Insurance Contracts | Level 2 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		8	10
Insurance Contracts | Level 3 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		73
Insurance Contracts | Level 3 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		5
Insurance Contracts | Fair Value, Inputs, Level 1, 2 and 3 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		212	162
Insurance Contracts | Fair Value, Inputs, Level 1, 2 and 3 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		13	10
Corporate debt instruments | Level 1 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		70	74
Corporate debt instruments | Level 1 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		183	4
Corporate debt instruments | Level 2 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		486	750
Corporate debt instruments | Level 2 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		30	36
Corporate debt instruments | Level 3 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		11
Corporate debt instruments | Level 3 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		1
Corporate debt instruments | Fair Value, Inputs, Level 1, 2 and 3 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		567	824
Corporate debt instruments | Fair Value, Inputs, Level 1, 2 and 3 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		214	40
Government securities | Level 1 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		16	43
Government securities | Level 1 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		165	3
Government securities | Level 2 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		1,303	1,720
Government securities | Level 2 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		82	100
Government securities | Fair Value, Inputs, Level 1, 2 and 3 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		1,319	1,763
Government securities | Fair Value, Inputs, Level 1, 2 and 3 | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value		247	103
Commingled funds/collective trust funds | NAV | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value	[3]	1,771	2,012
Commingled funds/collective trust funds | NAV | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value	[4]	495	725
Real Estate Funds | NAV | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value	[3]	37	67
Real Estate Funds | NAV | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value	[4]	9	11
Private Equity Funds | NAV | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value	[3]	1,304	1,395
Private Equity Funds | NAV | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value	[4]	147	173
Fixed Income Funds | NAV | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value	[3]	188	236
Fixed Income Funds | NAV | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value	[4]	12	14
Hedge Funds | NAV | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value	[3]	319	239
Hedge Funds | NAV | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value	[4]	20	14
Investments Measured At Fair Value Including Excluding Pending Purchases Sales And Accrued Income | NAV | Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total recorded at fair value	[4]	$ 683	$ 937

[1] Excludes net assets related to pending sales of securities and advanced subscription of $633 million, net accrued income of $21 million, and includes net assets related to pending purchases of securities of $16 million at December 31, 2024. Excludes net assets related to pending sales of securities of $298 million, net accrued income of $24 million, and includes net assets related to pending purchases of securities of $54 million at December 31, 2023.

[2] Excludes net assets related to pending sales of securities and advanced subscription of $19 million, net accrued income of $2 million, and includes net assets related to pending purchases of securities of $2 million at December 31, 2024. Excludes net assets related to pending sales of securities and advanced subscription of $17 million, net accrued income of $2 million, and includes net assets related to pending purchases of securities of $2 million at December 31, 2023.

[3] These investments that are measured at fair value using the NAV per share (or its equivalent) as a practical expedient are not required to be categorized in the fair value hierarchy.

[4] These investments that are measured at fair value using the NAV per share (or its equivalent) as a practical expedient are not required to be categorized in the fair value hierarchy.