Employee Benefit Plans - MEC - Unrecognized Amounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension | MEC
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Settlement	$ 3	$ (4)
Other Postretirement
Defined Benefit Plan Disclosure [Line Items]
Net loss (gain)	(88)	(38)
Prior service (credit) cost	20	21
Total	(68)	(16)	$ (33)
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	(16)	(33)
Net gain arising during the year	(54)	(4)
Settlement	0	0	0
Net amortization	2	1
Total	(52)	17
Ending balance	(68)	(16)	(33)
Other Postretirement | MEC
Defined Benefit Plan Disclosure [Line Items]
Net loss (gain)	(30)	11
Prior service (credit) cost	18	19
Total	(12)	30	(1)
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	30	(1)
Net gain arising during the year	(41)	9
Net prior service credit arising during the year		19
Settlement	0	0	0
Net amortization	(1)	3
Total	(42)	31
Ending balance	(12)	30	(1)
Other Postretirement | MEC | Regulatory Asset
Defined Benefit Plan Disclosure [Line Items]
Total	0	33	20
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	33	20
Net gain arising during the year	(33)	10
Net prior service credit arising during the year		0
Net amortization	0	3
Total	(33)	13
Ending balance	0	33	20
Other Postretirement | MEC | Regulatory Liability
Defined Benefit Plan Disclosure [Line Items]
Total	4	0	0
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	0	0
Net gain arising during the year	3	0
Net prior service credit arising during the year		0
Net amortization	1	0
Total	4	0
Ending balance	4	0	0
Other Postretirement | MEC | Receivables (Payables) With Affiliates
Defined Benefit Plan Disclosure [Line Items]
Total	(16)	(3)	(21)
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	(3)	(21)
Net gain arising during the year	(11)	(1)
Net prior service credit arising during the year		19
Net amortization	(2)	0
Total	(13)	18
Ending balance	(16)	(3)	(21)
U.S. | Pension
Defined Benefit Plan Disclosure [Line Items]
Net loss (gain)	325	365
Prior service (credit) cost	(3)	(4)
Total	344	390	353
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	390	353
Net gain arising during the year	(35)	76
Settlement	3	(17)	(3)
Net amortization	(14)	(19)
Total	(46)	37
Ending balance	344	390	353
U.S. | Pension | MEC
Defined Benefit Plan Disclosure [Line Items]
Net loss (gain)	(19)	(4)
Prior service (credit) cost	(3)	(3)
Total	(22)	(7)	(25)
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	(7)	(25)
Net gain arising during the year	(18)	26
Net prior service credit arising during the year		(3)
Settlement	3	(4)	5
Net amortization		(1)
Total	(15)	18
Ending balance	(22)	(7)	(25)
U.S. | Pension | MEC | Regulatory Asset
Defined Benefit Plan Disclosure [Line Items]
Total	16	14	22
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	14	22
Net gain arising during the year	2	(7)
Net prior service credit arising during the year		0
Settlement	0	0
Net amortization		(1)
Total	2	(8)
Ending balance	16	14	22
U.S. | Pension | MEC | Regulatory Liability
Defined Benefit Plan Disclosure [Line Items]
Total	(20)	(1)	(55)
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	(1)	(55)
Net gain arising during the year	(22)	58
Net prior service credit arising during the year		0
Settlement	3	(4)
Net amortization		0
Total	(19)	54
Ending balance	(20)	(1)	(55)
U.S. | Pension | MEC | Receivables (Payables) With Affiliates
Defined Benefit Plan Disclosure [Line Items]
Total	(18)	(20)	8
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	(20)	8
Net gain arising during the year	2	(25)
Net prior service credit arising during the year		(3)
Settlement	0	0
Net amortization		0
Total	2	(28)
Ending balance	$ (18)	$ (20)	$ 8