Fair Value of Financial Instruments Financial Assets and Liabilities Recognized at Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Assets:
Cash equivalents	$ 0	$ 150
Debt securities:
Domestic government	19	19
Corporate credit	10	9
Money market funds measured at NAV (2)	6	11
Non-qualified benefit plan trust: (2)
Money market funds	2	1
Equity securities - domestic	2	3
Debt securities—domestic government	3	3
Assets from price risk management activities: (1) (3)
Electricity	52	156
Natural gas	46	231
Total	6	11
Assets, Fair Value Disclosure	140	583
Liabilities from price risk management activities: (1) (3)
Electricity	177	146
Natural gas	80	47
Total	257	193
Fair Value, Inputs, Level 1 [Member]
Assets:
Cash equivalents	0	150
Debt securities:
Domestic government	9	9
Corporate credit	0	0
Non-qualified benefit plan trust: (2)
Money market funds	2	1
Equity securities - domestic	2	3
Debt securities—domestic government	3	3
Assets from price risk management activities: (1) (3)
Electricity	0	0
Natural gas	0	0
Total	16	166
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	10	10
Corporate credit	10	9
Non-qualified benefit plan trust: (2)
Money market funds	0	0
Equity securities - domestic	0	0
Debt securities—domestic government	0	0
Assets from price risk management activities: (1) (3)
Electricity	29	93
Natural gas	43	225
Total	92	337
Liabilities from price risk management activities: (1) (3)
Electricity	36	53
Natural gas	57	39
Total	93	92
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
Equity securities - domestic	0	0
Debt securities—domestic government	0	0
Assets from price risk management activities: (1) (3)
Electricity	23	63
Natural gas	3	6
Total	26	69
Liabilities from price risk management activities: (1) (3)
Electricity	141	93
Natural gas	23	8
Total	$ 164	$ 101