Employee Benefit Plans - Fair Value Measurements (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Other Postretirement
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 691	$ 665	$ 614
Other Postretirement | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	267	271	264
Other Postretirement | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	557	532
Other Postretirement | Level 1, 2 and 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	133	138
Other Postretirement | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	409	372
Other Postretirement | Level 1 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	23	21
Other Postretirement | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	148	160
Other Postretirement | Level 2 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	110	117
Other Postretirement | Level 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | Cash equivalents | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	22	22
Other Postretirement | Cash equivalents | Level 1, 2 and 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	6	7
Other Postretirement | Cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	9	13
Other Postretirement | Cash equivalents | Level 1 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	4
Other Postretirement | Cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	13	9
Other Postretirement | Cash equivalents | Level 2 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	6	3
Other Postretirement | Cash equivalents | Level 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | U.S. government obligations | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	18	11
Other Postretirement | U.S. government obligations | Level 1, 2 and 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	16	9
Other Postretirement | U.S. government obligations | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	18	11
Other Postretirement | U.S. government obligations | Level 1 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	16	9
Other Postretirement | U.S. government obligations | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | U.S. government obligations | Level 2 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | U.S. government obligations | Level 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | Corporate obligations | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	37	50
Other Postretirement | Corporate obligations | Level 1, 2 and 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	34	45
Other Postretirement | Corporate obligations | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | Corporate obligations | Level 1 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | Corporate obligations | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	37	50
Other Postretirement | Corporate obligations | Level 2 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	34	45
Other Postretirement | Corporate obligations | Level 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | Municipal obligations | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	43	45
Other Postretirement | Municipal obligations | Level 1, 2 and 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	18	19
Other Postretirement | Municipal obligations | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | Municipal obligations | Level 1 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | Municipal obligations | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	43	45
Other Postretirement | Municipal obligations | Level 2 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	18	19
Other Postretirement | Municipal obligations | Level 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | Agency, asset and mortgage-backed obligations | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	55	56
Other Postretirement | Agency, asset and mortgage-backed obligations | Level 1, 2 and 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	52	50
Other Postretirement | Agency, asset and mortgage-backed obligations | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | Agency, asset and mortgage-backed obligations | Level 1 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | Agency, asset and mortgage-backed obligations | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	55	56
Other Postretirement | Agency, asset and mortgage-backed obligations | Level 2 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	52	50
Other Postretirement | Agency, asset and mortgage-backed obligations | Level 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | Equity securities, U.S. companies | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	7	8
Other Postretirement | Equity securities, U.S. companies | Level 1, 2 and 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	7	8
Other Postretirement | Equity securities, U.S. companies | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	7	8
Other Postretirement | Equity securities, U.S. companies | Level 1 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	7	8
Other Postretirement | Equity securities, U.S. companies | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | Equity securities, U.S. companies | Level 2 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | Equity securities, U.S. companies | Level 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 0	$ 0
Other Postretirement | Investment funds
Defined Benefit Plan Disclosure [Line Items]
Percentage of funds comprised of equity securities	59.00%	55.00%
Percentage of funds comprised of debt securities	41.00%	45.00%
Percentage of funds invested in United States securities	88.00%	88.00%
Percentage of funds invested in international securities	12.00%	12.00%
Other Postretirement | Investment funds | PAC
Defined Benefit Plan Disclosure [Line Items]
Percentage of funds comprised of equity securities	39.00%	38.00%
Percentage of funds comprised of debt securities	61.00%	62.00%
Percentage of funds invested in United States securities	90.00%	89.00%
Percentage of funds invested in international securities	10.00%	11.00%
Other Postretirement | Investment funds | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 375	$ 340
Other Postretirement | Investment funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	375	340
Other Postretirement | Investment funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | Investment funds | NAV
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	134	133
Other Postretirement | Investment funds | NAV | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	134	133
U.S. | Pension
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	2,010	2,069	2,013
U.S. | Pension | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	728	764	758
U.S. | Pension | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	1,127	1,123
U.S. | Pension | Level 1, 2 and 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	421	428
U.S. | Pension | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	337	319
U.S. | Pension | Level 1 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	124	105
U.S. | Pension | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	790	804
U.S. | Pension | Level 2 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	297	323
U.S. | Pension | Level 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | Cash equivalents | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	15	40
U.S. | Pension | Cash equivalents | Level 1, 2 and 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	3	28
U.S. | Pension | Cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | Cash equivalents | Level 1 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | Cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	15	40
U.S. | Pension | Cash equivalents | Level 2 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	3	28
U.S. | Pension | Cash equivalents | Level 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | U.S. government obligations | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	156	129
U.S. | Pension | U.S. government obligations | Level 1, 2 and 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	59	52
U.S. | Pension | U.S. government obligations | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	156	129
U.S. | Pension | U.S. government obligations | Level 1 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	59	52
U.S. | Pension | U.S. government obligations | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | U.S. government obligations | Level 2 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | U.S. government obligations | Level 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | Corporate obligations | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	639	620
U.S. | Pension | Corporate obligations | Level 1, 2 and 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	229	232
U.S. | Pension | Corporate obligations | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | Corporate obligations | Level 1 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | Corporate obligations | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	639	620
U.S. | Pension | Corporate obligations | Level 2 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	229	232
U.S. | Pension | Corporate obligations | Level 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | Municipal obligations | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	33	40
U.S. | Pension | Municipal obligations | Level 1, 2 and 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	13	16
U.S. | Pension | Municipal obligations | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | Municipal obligations | Level 1 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | Municipal obligations | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	33	40
U.S. | Pension | Municipal obligations | Level 2 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	13	16
U.S. | Pension | Municipal obligations | Level 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | Agency, asset and mortgage-backed obligations | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	103	104
U.S. | Pension | Agency, asset and mortgage-backed obligations | Level 1, 2 and 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	52	47
U.S. | Pension | Agency, asset and mortgage-backed obligations | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | Agency, asset and mortgage-backed obligations | Level 1 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | Agency, asset and mortgage-backed obligations | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	103	104
U.S. | Pension | Agency, asset and mortgage-backed obligations | Level 2 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	52	47
U.S. | Pension | Agency, asset and mortgage-backed obligations | Level 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | Equity securities, U.S. companies | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	180	189
U.S. | Pension | Equity securities, U.S. companies | Level 1, 2 and 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	65	53
U.S. | Pension | Equity securities, U.S. companies | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	180	189
U.S. | Pension | Equity securities, U.S. companies | Level 1 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	65	53
U.S. | Pension | Equity securities, U.S. companies | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | Equity securities, U.S. companies | Level 2 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | Equity securities, U.S. companies | Level 3 | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
U.S. | Pension | Equity securities, international companies | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	1	1
U.S. | Pension | Equity securities, international companies | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	1	1
U.S. | Pension | Equity securities, international companies | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 0	$ 0
U.S. | Pension | Investment funds
Defined Benefit Plan Disclosure [Line Items]
Percentage of funds comprised of equity securities	53.00%	51.00%
Percentage of funds comprised of debt securities	47.00%	49.00%
Percentage of funds invested in United States securities	94.00%	94.00%
Percentage of funds invested in international securities	6.00%	6.00%
U.S. | Pension | Investment funds | PAC
Defined Benefit Plan Disclosure [Line Items]
Percentage of funds comprised of equity securities	40.00%	41.00%
Percentage of funds comprised of debt securities	60.00%	59.00%
Percentage of funds invested in United States securities	88.00%
Percentage of funds invested in international securities	12.00%
U.S. | Pension | Investment funds | NAV
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 861	$ 920
U.S. | Pension | Investment funds | NAV | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	285	310
U.S. | Pension | Limited partnership interests | NAV
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	22	26
U.S. | Pension | Limited partnership interests | NAV | PAC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	22	26
United Kingdom | Pension
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	1,242	1,402	$ 1,363
United Kingdom | Pension | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	1,155	1,283
United Kingdom | Pension | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	429	587
United Kingdom | Pension | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	592	560
United Kingdom | Pension | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	134	136
United Kingdom | Pension | Cash equivalents | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	23	36
United Kingdom | Pension | Cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	1	8
United Kingdom | Pension | Cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	22	28
United Kingdom | Pension | Cash equivalents | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
United Kingdom | Pension | United Kingdom government | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	428	579
United Kingdom | Pension | United Kingdom government | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	428	579
United Kingdom | Pension | United Kingdom government | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
United Kingdom | Pension | United Kingdom government | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 0	$ 0
United Kingdom | Pension | Investment funds
Defined Benefit Plan Disclosure [Line Items]
Percentage of funds comprised of equity securities	10.00%	14.00%
Percentage of funds comprised of debt securities	90.00%	86.00%
United Kingdom | Pension | Investment funds | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 570	$ 532
United Kingdom | Pension | Investment funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
United Kingdom | Pension | Investment funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	570	532
United Kingdom | Pension | Investment funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
United Kingdom | Pension | Investment funds | NAV
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	87	119
United Kingdom | Pension | Real estate funds | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	134	136
United Kingdom | Pension | Real estate funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
United Kingdom | Pension | Real estate funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
United Kingdom | Pension | Real estate funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 134	$ 136