Fair Value of Financial Instruments Financial Assets and Liabilities Recognized at Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Assets:
Cash equivalents	$ 0	$ 150
Debt securities:
Domestic government	20	19
Corporate credit	11	9
Money market funds measured at NAV (2)	7	11
Non-qualified benefit plan trust: (2)
Money market funds	3	1
Equity securities - domestic	3	3
Debt securities—domestic government	3	3
Assets from price risk management activities: (1) (3)
Electricity	84	156
Natural gas	77	231
Total	7	11
Assets, Fair Value Disclosure	208	583
Liabilities from price risk management activities: (1) (3)
Electricity	113	146
Natural gas	57	47
Total	170	193
Fair Value, Inputs, Level 1 [Member]
Assets:
Cash equivalents	0	150
Debt securities:
Domestic government	10	9
Corporate credit	0	0
Non-qualified benefit plan trust: (2)
Money market funds	3	1
Equity securities - domestic	3	3
Debt securities—domestic government	3	3
Assets from price risk management activities: (1) (3)
Electricity	0	0
Natural gas	0	0
Total	19	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	11	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	39	93
Natural gas	71	225
Total	131	337
Liabilities from price risk management activities: (1) (3)
Electricity	41	53
Natural gas	50	39
Total	91	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	45	63
Natural gas	6	6
Total	51	69
Liabilities from price risk management activities: (1) (3)
Electricity	72	93
Natural gas	7	8
Total	$ 79	$ 101