Fair Value of Financial Instruments Financial Assets and Liabilities Recognized at Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Assets:
Cash equivalents	$ 173	$ 0
Debt securities:
Domestic government	16	18
Corporate credit	7	7
Money market funds measured at NAV (2)	7	6
Non-qualified benefit plan trust: (2)
Money market funds	2	2
Debt securities—domestic government	3	3
Assets from price risk management activities: (1) (3)
Electricity	26	22
Natural gas	11	11
Total	10	9
Assets, Fair Value Disclosure	248	72
Liabilities from price risk management activities: (1) (3)
Electricity	61	73
Natural gas	132	166
Total	193	239
Fair Value, Inputs, Level 1 [Member]
Assets:
Cash equivalents	173	0
Debt securities:
Domestic government	8	9
Corporate credit	0	0
Non-qualified benefit plan trust: (2)
Money market funds	2	2
Debt securities—domestic government	3	3
Assets from price risk management activities: (1) (3)
Electricity	0	0
Natural gas	0	0
Total	186	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	8	9
Corporate credit	7	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	20	8
Natural gas	11	11
Total	46	35
Liabilities from price risk management activities: (1) (3)
Electricity	28	30
Natural gas	116	150
Total	144	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	6	14
Natural gas	0	0
Total	6	14
Liabilities from price risk management activities: (1) (3)
Electricity	33	43
Natural gas	16	16
Total	$ 49	$ 59