Fair Value of Financial Instruments Financial Assets and Liabilities Recognized at Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Assets:
Cash equivalents	$ 0	$ 0
Debt securities:
Domestic government	20	18
Corporate credit	8	7
Money market funds measured at NAV (2)	7	6
Non-qualified benefit plan trust: (2)
Money market funds	1	2
Alternative Investment	4	3
Debt securities—domestic government	2	3
Assets from price risk management activities: (1) (3)
Electricity	11	22
Natural gas	10	11
Total	11	9
Assets, Fair Value Disclosure	63	72
Liabilities from price risk management activities: (1) (3)
Electricity	45	73
Natural gas	143	166
Total	188	239
Fair Value, Inputs, Level 1 [Member]
Assets:
Cash equivalents	0	0
Debt securities:
Domestic government	11	9
Corporate credit	0	0
Non-qualified benefit plan trust: (2)
Money market funds	1	2
Debt securities—domestic government	2	3
Assets from price risk management activities: (1) (3)
Electricity	0	0
Natural gas	0	0
Total	14	14
Liabilities from price risk management activities: (1) (3)
Electricity	0	0
Natural gas	0	0
Total	0	0
Fair Value, Inputs, Level 2 [Member]
Assets:
Cash equivalents	0	0
Debt securities:
Domestic government	9	9
Corporate credit	8	7
Non-qualified benefit plan trust: (2)
Money market funds	0	0
Debt securities—domestic government	0	0
Assets from price risk management activities: (1) (3)
Electricity	11	8
Natural gas	10	11
Total	38	35
Liabilities from price risk management activities: (1) (3)
Electricity	15	30
Natural gas	111	150
Total	126	180
Fair Value, Inputs, Level 3 [Member]
Assets:
Cash equivalents	0	0
Debt securities:
Domestic government	0	0
Corporate credit	0	0
Non-qualified benefit plan trust: (2)
Money market funds	0	0
Debt securities—domestic government	0	0
Assets from price risk management activities: (1) (3)
Electricity	0	14
Natural gas	0	0
Total	0	14
Liabilities from price risk management activities: (1) (3)
Electricity	30	43
Natural gas	32	16
Total	$ 62	$ 59