Employee Benefit Plans - MEC - Unrecognized Amounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Other Postretirement
Defined Benefit Plan Disclosure [Line Items]
Net loss (gain)	$ (34)	$ 34
Prior service credit	(1)	(9)
Total	(33)	28
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	28	(31)
Net (gain) loss arising during the year	(65)	55
Net amortization	3	4
Total	(61)	59
Ending balance	(33)	28
Other Postretirement | Regulatory Asset
Defined Benefit Plan Disclosure [Line Items]
Total	11	47
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	47	4
Net (gain) loss arising during the year	(40)	36
Net amortization	3	7
Total	(36)	43
Ending balance	11	47
Other Postretirement | Regulatory Liability
Defined Benefit Plan Disclosure [Line Items]
Total	(45)	(23)
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	(23)	(32)
Net (gain) loss arising during the year	(22)	12
Net amortization	0	(3)
Total	(22)	9
Ending balance	(45)	(23)
Other Postretirement | MEC
Defined Benefit Plan Disclosure [Line Items]
Net loss (gain)	2	45
Prior service credit	(3)	(9)
Total	(1)	36
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	36	(10)
Net (gain) loss arising during the year	(42)	41
Net prior service credit arising during the year	1
Net amortization	4	5
Total	(37)	46
Ending balance	(1)	36
Other Postretirement | MEC | Regulatory Asset
Defined Benefit Plan Disclosure [Line Items]
Total	20	45
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	45	7
Net (gain) loss arising during the year	(29)	34
Net prior service credit arising during the year	1
Net amortization	3	4
Total	(25)	38
Ending balance	20	45
Other Postretirement | MEC | Receivables (Payables) With Affiliates
Defined Benefit Plan Disclosure [Line Items]
Total	(21)	(9)
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	(9)	(17)
Net (gain) loss arising during the year	(13)	7
Net prior service credit arising during the year	0
Net amortization	1	1
Total	(12)	8
Ending balance	(21)	(9)
United States | Pension
Defined Benefit Plan Disclosure [Line Items]
Net loss (gain)	343	612
Prior service credit	(1)	(1)
Total	353	613
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	613	652
Net (gain) loss arising during the year	(231)	(7)
Net amortization	(25)	(32)
Settlement	(4)
Total	(260)	(39)
Ending balance	353	613
United States | Pension | Regulatory Asset
Defined Benefit Plan Disclosure [Line Items]
Total	390	600
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	600	661
Net (gain) loss arising during the year	(177)	(30)
Net amortization	(24)	(31)
Settlement	(9)
Total	(210)	(61)
Ending balance	390	600
United States | Pension | Regulatory Liability
Defined Benefit Plan Disclosure [Line Items]
Total	(59)	(20)
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	(20)	(33)
Net (gain) loss arising during the year	(44)	13
Net amortization	0	0
Settlement	5
Total	(39)	13
Ending balance	(59)	(20)
United States | Pension | MEC
Defined Benefit Plan Disclosure [Line Items]
Net loss (gain)	(25)	18
Prior service credit	0	0
Total	(25)	18
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	18	5
Net (gain) loss arising during the year	(47)	14
Net amortization	(1)	(1)
Settlement	5
Total	(43)	13
Ending balance	(25)	18
United States | Pension | MEC | Regulatory Asset
Defined Benefit Plan Disclosure [Line Items]
Total	22	21
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	21	19
Net (gain) loss arising during the year	2	3
Net amortization	(1)	(1)
Settlement	0
Total	1	2
Ending balance	22	21
United States | Pension | MEC | Regulatory Liability
Defined Benefit Plan Disclosure [Line Items]
Total	(55)	(20)
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	(20)	(32)
Net (gain) loss arising during the year	(40)	12
Net amortization	0	0
Settlement	5
Total	(35)	12
Ending balance	(55)	(20)
United States | Pension | MEC | Receivables (Payables) With Affiliates
Defined Benefit Plan Disclosure [Line Items]
Total	8	17
Defined Benefit Plan, Reconciliation of Amounts Not Yet Recognized As Components of Net Periodic Benefit Cost [Roll Forward]
Beginning balance	17	18
Net (gain) loss arising during the year	(9)	(1)
Net amortization	0	0
Settlement	0
Total	(9)	(1)
Ending balance	$ 8	$ 17