Employee Benefit Plans - MEC - Fair Value Measurements (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Pension | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 2,013	$ 2,795	$ 2,824
Pension | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	1,096	1,412
Pension | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	308	277
Pension | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	788	1,135
Pension | Cash equivalents | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	51	64
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	51	64
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	109	142
Pension | U.S. government obligations | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	109	142
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	613	912
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	613	912
Pension | Municipal obligations | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	43	66
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	43	66
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	81	93
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	81	93
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	198	135
Pension | Equity securities, U.S. companies | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	198	135
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
Pension | Equity securities, international companies | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	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
Pension | Investment funds | U.S.
Defined Benefit Plan Disclosure [Line Items]
Percentage of funds comprised of equity securities	53.00%	54.00%
Percentage of funds comprised of debt securities	47.00%	46.00%
Percentage of funds invested in United States securities	95.00%	89.00%
Percentage of funds invested in international securities	5.00%	11.00%
Pension | Investment funds | NAV | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 885	$ 1,349
Pension | MEC | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	490	704	718
Pension | MEC | Level 1, 2 and 3 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	267	372
Pension | MEC | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	94	68
Pension | MEC | Level 2 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	173	304
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	15	27
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	15	27
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	22	33
Pension | MEC | U.S. government obligations | Level 1 | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	22	33
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	135	242
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	135	242
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	10	18
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	10	18
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	13	17
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	13	17
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	71	35
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	71	35
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
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
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
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
Pension | MEC | Investment funds | U.S.
Defined Benefit Plan Disclosure [Line Items]
Percentage of funds comprised of equity securities	55.00%	56.00%
Percentage of funds comprised of debt securities	45.00%	44.00%
Percentage of funds invested in United States securities	97.00%	90.00%
Percentage of funds invested in international securities	3.00%	10.00%
Pension | MEC | Investment funds | NAV | U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 223	$ 332
Other Postretirement
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	614	769	744
Other Postretirement | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	482	607
Other Postretirement | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	337	437
Other Postretirement | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	145	170
Other Postretirement | Cash equivalents | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	24	16
Other Postretirement | Cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	15	12
Other Postretirement | Cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	9	4
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	8	27
Other Postretirement | U.S. government obligations | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	8	27
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	52	85
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	52	85
Other Postretirement | Municipal obligations | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	35	43
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	35	43
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	49	38
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	49	38
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	4
Other Postretirement | Equity securities, U.S. companies | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	7	4
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	55.00%	55.00%
Percentage of funds comprised of debt securities	45.00%	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	$ 307	$ 394
Other Postretirement | Investment funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	307	394
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	132	161
Other Postretirement | MEC
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	240	308	$ 278
Other Postretirement | MEC | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	240	308
Other Postretirement | MEC | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	213	271
Other Postretirement | MEC | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	27	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	10	8
Other Postretirement | MEC | Cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	10	8
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	3
Other Postretirement | MEC | U.S. government obligations | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	2	3
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	6
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	6
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	22	28
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	22	28
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	2	3
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	2	3
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	82.00%	82.00%
Percentage of funds comprised of debt securities	18.00%	18.00%
Percentage of funds invested in United States securities	82.00%	82.00%
Percentage of funds invested in international securities	18.00%	18.00%
Other Postretirement | MEC | Investment funds | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	$ 201	$ 260
Other Postretirement | MEC | Investment funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value, end of year	201	260
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