Fair Value of Financial Instruments Financial Assets and Liabilities Recognized at Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Assets:
Cash equivalents	$ 0	$ 150
Debt securities:
Domestic government	17	19
Corporate credit	8	9
Money market funds measured at NAV (2)	9	11
Non-qualified benefit plan trust: (2)
Money market funds	1	1
Equity securities - domestic	0	3
Debt securities—domestic government	3	3
Assets from price risk management activities: (1) (3)
Electricity	31	156
Natural gas	67	231
Total	9	11
Assets, Fair Value Disclosure	136	583
Liabilities from price risk management activities: (1) (3)
Electricity	122	146
Natural gas	71	47
Total	193	193
Fair Value, Inputs, Level 1 [Member]
Assets:
Cash equivalents	0	150
Debt securities:
Domestic government	8	9
Corporate credit	0	0
Non-qualified benefit plan trust: (2)
Money market funds	1	1
Equity securities - domestic	0	3
Debt securities—domestic government	3	3
Assets from price risk management activities: (1) (3)
Electricity	0	0
Natural gas	0	0
Total	12	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	9	10
Corporate credit	8	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	18	93
Natural gas	64	225
Total	99	337
Liabilities from price risk management activities: (1) (3)
Electricity	10	53
Natural gas	50	39
Total	60	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	13	63
Natural gas	3	6
Total	16	69
Liabilities from price risk management activities: (1) (3)
Electricity	112	93
Natural gas	21	8
Total	$ 133	$ 101