Long-term Debt - MEC (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Par value	$ 55,471
Subsidiary debt, current	2,646	$ 2,740
Subsidiary debt, noncurrent	41,154	36,231
Maturity Schedule
2025	2,646
2026	1,366
2027	860
2028	1,267
2029	3,315
2030 and thereafter	46,017
MEC
Debt Instrument [Line Items]
Par value	8,937
Subsidiary debt	8,824	8,766
Subsidiary debt, current	17	539
Subsidiary debt, noncurrent	8,807	8,227
Maturity Schedule
2025	17
2026	4
2027	379
2028	4
2029	854
2030 and thereafter	$ 7,679
MEC | Committed common equity percentage to regulators
Maturity Schedule
Common equity to total capitalization percentage	42.00%
MEC | Committed common equity percentage to regulators beyond companies control
Maturity Schedule
Common equity to total capitalization percentage below which reasonable efforts to maintain agreed to percentage is not required	39.00%
MEC | Common equity level to total capitalization
Maturity Schedule
Common equity level to total capitalization	51.00%
MEC | Dividend restriction for common equity commitment
Maturity Schedule
Amount available for dividend distribution	$ 3,800
3.50%, due 2024 | MEC
Debt Instrument [Line Items]
Stated rate	3.50%
Par value	$ 0
Subsidiary debt	$ 0	500
3.10%, due 2027 | MEC
Debt Instrument [Line Items]
Stated rate	3.10%
Par value	$ 375
Subsidiary debt	$ 374	374
3.65%, due 2029 | MEC
Debt Instrument [Line Items]
Stated rate	3.65%
Par value	$ 850
Subsidiary debt	$ 857	858
5.35%, due 2034 | MEC
Debt Instrument [Line Items]
Stated rate	5.35%
Par value	$ 350
Subsidiary debt	$ 347	347
4.80%, due 2043 | MEC
Debt Instrument [Line Items]
Stated rate	4.80%
Par value	$ 350
Subsidiary debt	$ 347	347
4.40%, due 2044 | MEC
Debt Instrument [Line Items]
Stated rate	4.40%
Par value	$ 400
Subsidiary debt	$ 396	396
4.25%, due 2046 | MEC
Debt Instrument [Line Items]
Stated rate	4.25%
Par value	$ 450
Subsidiary debt	$ 446	446
3.95%, due 2047 | MEC
Debt Instrument [Line Items]
Stated rate	3.95%
Par value	$ 475
Subsidiary debt	$ 471	471
3.65%, due 2048 | MEC
Debt Instrument [Line Items]
Stated rate	3.65%
Par value	$ 700
Subsidiary debt	$ 690	690
4.25%, due 2049 | MEC
Debt Instrument [Line Items]
Stated rate	4.25%
Par value	$ 900
Subsidiary debt	$ 876	876
3.15%, due 2050 | MEC
Debt Instrument [Line Items]
Stated rate	3.15%
Par value	$ 600
Subsidiary debt	$ 593	592
2.70%, due 2052 | MEC
Debt Instrument [Line Items]
Stated rate	2.70%
Par value	$ 500
Subsidiary debt	$ 493	492
5.85%, due 2054 | MEC
Debt Instrument [Line Items]
Stated rate	5.85%
Par value	$ 1,000
Subsidiary debt	$ 990	989
5.30%, due 2055 | MEC
Debt Instrument [Line Items]
Stated rate	5.30%
Par value	$ 600
Subsidiary debt	$ 592	0
6.75% Series, due 2031 | MEC
Debt Instrument [Line Items]
Stated rate	6.75%
Par value	$ 400
Subsidiary debt	$ 398	398
5.75% Series, due 2035 | MEC
Debt Instrument [Line Items]
Stated rate	5.75%
Par value	$ 300
Subsidiary debt	$ 299	299
5.80% Series, due 2036 | MEC
Debt Instrument [Line Items]
Stated rate	5.80%
Par value	$ 350
Subsidiary debt	348	348
Transmission upgrade obligation, 3.30% to 7.90%, due 2036 to 2043 | MEC
Debt Instrument [Line Items]
Par value	66
Subsidiary debt	$ 37	$ 39
Transmission upgrade obligation, 3.30% to 7.90%, due 2036 to 2043 | MEC | Minimum
Debt Instrument [Line Items]
Vendor financing, discount rate applied	3.303%
Transmission upgrade obligation, 3.30% to 7.90%, due 2036 to 2043 | MEC | Maximum
Debt Instrument [Line Items]
Vendor financing, discount rate applied	7.896%
Variable-rate tax-exempt bond obligation series: (weighted average interest rate- 2024-3.359%, 2023-4.807%): | MEC
Debt Instrument [Line Items]
Variable rate	3.359%	4.807%
Due 2024 | MEC
Debt Instrument [Line Items]
Par value	$ 0
Subsidiary debt	0	$ 35
Due 2025 | MEC
Debt Instrument [Line Items]
Par value	13
Subsidiary debt	13	13
Due 2036 | MEC
Debt Instrument [Line Items]
Par value	33
Subsidiary debt	33	33
Due 2038 | MEC
Debt Instrument [Line Items]
Par value	45
Subsidiary debt	45	45
Due 2046 | MEC
Debt Instrument [Line Items]
Par value	30
Subsidiary debt	30	29
Due 2047 | MEC
Debt Instrument [Line Items]
Par value	150
Subsidiary debt	$ 149	$ 149