Employee Benefit Plans - MEC - Fair Value Measurements (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Pension | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 2,010	$ 2,069	$ 2,013
Pension | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	1,127	1,123
Pension | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	337	319
Pension | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	790	804
Pension | Cash equivalents | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	15	40
Pension | Cash equivalents | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | Cash equivalents | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	15	40
Pension | U.S. government obligations | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	156	129
Pension | U.S. government obligations | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	156	129
Pension | U.S. government obligations | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | Corporate obligations | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	639	620
Pension | Corporate obligations | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | Corporate obligations | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	639	620
Pension | Municipal obligations | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	33	40
Pension | Municipal obligations | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | Municipal obligations | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	33	40
Pension | Agency, asset and mortgage-backed obligations | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	103	104
Pension | Agency, asset and mortgage-backed obligations | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | Agency, asset and mortgage-backed obligations | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	103	104
Pension | Equity securities, U.S. companies | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	180	189
Pension | Equity securities, U.S. companies | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	180	189
Pension | Equity securities, U.S. companies | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | Equity securities, international companies | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	1	1
Pension | Equity securities, international companies | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	1	1
Pension | Equity securities, international companies | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 0	$ 0
Pension | Investment funds | U.S.
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%
Pension | Investment funds | NAV | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 861	$ 920
Pension | MEC | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	522	516	490
Pension | MEC | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	229	232
Pension | MEC | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	81	91
Pension | MEC | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	148	141
Pension | MEC | Level 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | MEC | Cash equivalents | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	11	11
Pension | MEC | Cash equivalents | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | MEC | Cash equivalents | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	11	11
Pension | MEC | Cash equivalents | Level 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | MEC | U.S. government obligations | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	27	25
Pension | MEC | U.S. government obligations | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	27	25
Pension | MEC | U.S. government obligations | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | MEC | U.S. government obligations | Level 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | MEC | Corporate obligations | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	117	110
Pension | MEC | Corporate obligations | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | MEC | Corporate obligations | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	117	110
Pension | MEC | Corporate obligations | Level 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | MEC | Municipal obligations | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	5	6
Pension | MEC | Municipal obligations | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | MEC | Municipal obligations | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	5	6
Pension | MEC | Municipal obligations | Level 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | MEC | Agency, asset and mortgage-backed obligations | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	15	14
Pension | MEC | Agency, asset and mortgage-backed obligations | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | MEC | Agency, asset and mortgage-backed obligations | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	15	14
Pension | MEC | Agency, asset and mortgage-backed obligations | Level 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | MEC | Equity securities, U.S. companies | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	53	65
Pension | MEC | Equity securities, U.S. companies | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	53	65
Pension | MEC | Equity securities, U.S. companies | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | MEC | Equity securities, U.S. companies | Level 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | MEC | Equity securities, international companies | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	1	1
Pension | MEC | Equity securities, international companies | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	1	1
Pension | MEC | Equity securities, international companies | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Pension | MEC | Equity securities, international companies | Level 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 0	$ 0
Pension | MEC | Investment funds | U.S.
Defined Benefit Plan Disclosure [Line Items]
Percentage of funds comprised of equity securities	71.00%	68.00%
Percentage of funds comprised of debt securities	29.00%	32.00%
Percentage of funds invested in United States securities	94.00%	93.00%
Percentage of funds invested in international securities	6.00%	7.00%
Pension | MEC | Investment funds | NAV | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 293	$ 284
Other Postretirement
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	691	665	614
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
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	409	372
Other Postretirement | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	148	160
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
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	9	13
Other Postretirement | Cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	13	9
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
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	18	11
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 | 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
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 | 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
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 | 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
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 | 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
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 | 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 | 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 | MEC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	306	278	$ 240
Other Postretirement | MEC | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	306	278
Other Postretirement | MEC | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	275	241
Other Postretirement | MEC | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	31	37
Other Postretirement | MEC | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | MEC | Cash equivalents | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	9	9
Other Postretirement | MEC | Cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	9	9
Other Postretirement | MEC | Cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | MEC | Cash equivalents | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | MEC | U.S. government obligations | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	2	2
Other Postretirement | MEC | U.S. government obligations | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	2	2
Other Postretirement | MEC | U.S. government obligations | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | MEC | U.S. government obligations | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | MEC | Corporate obligations | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	3	5
Other Postretirement | MEC | Corporate obligations | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | MEC | Corporate obligations | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	3	5
Other Postretirement | MEC | Corporate obligations | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | MEC | Municipal obligations | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	25	26
Other Postretirement | MEC | Municipal obligations | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | MEC | Municipal obligations | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	25	26
Other Postretirement | MEC | Municipal obligations | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | MEC | 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	3	6
Other Postretirement | MEC | 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 | MEC | Agency, asset and mortgage-backed obligations | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	3	6
Other Postretirement | MEC | Agency, asset and mortgage-backed obligations | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 0	$ 0
Other Postretirement | MEC | Investment funds
Defined Benefit Plan Disclosure [Line Items]
Percentage of funds comprised of equity securities	84.00%	83.00%
Percentage of funds comprised of debt securities	16.00%	17.00%
Percentage of funds invested in United States securities	84.00%	83.00%
Percentage of funds invested in international securities	16.00%	17.00%
Other Postretirement | MEC | Investment funds | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 264	$ 230
Other Postretirement | MEC | Investment funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	264	230
Other Postretirement | MEC | Investment funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	0	0
Other Postretirement | MEC | Investment funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 0	$ 0