Fair Value of Financial Instruments Financial Assets and Liabilities Recognized at Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Assets:
Cash equivalents	$ 63	$ 44
Debt securities:
Domestic government	17	19
Corporate credit	12	14
Money market funds measured at NAV (2)	14	14
Non-qualified benefit plan trust: (2)
Money market funds	1	1
Equity securities - domestic	3	4
Debt securities—domestic government	3	4
Assets from price risk management activities: (1) (3)
Electricity	50	17
Natural gas	261	120
Total	14	14
Assets, Fair Value Disclosure	424	237
Liabilities from price risk management activities: (1) (3)
Electricity	114	123
Natural gas	8	14
Total	122	137
Fair Value, Inputs, Level 1 [Member]
Assets:
Cash equivalents	63	44
Debt securities:
Domestic government	9	9
Corporate credit	0	0
Non-qualified benefit plan trust: (2)
Money market funds	1	1
Equity securities - domestic	3	4
Debt securities—domestic government	3	4
Assets from price risk management activities: (1) (3)
Electricity	0	0
Natural gas	0	0
Total	79	62
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	10
Corporate credit	12	14
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	16
Natural gas	235	115
Total	294	155
Liabilities from price risk management activities: (1) (3)
Electricity	43	33
Natural gas	7	13
Total	50	46
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	11	1
Natural gas	26	5
Total	37	6
Liabilities from price risk management activities: (1) (3)
Electricity	71	90
Natural gas	1	1
Total	$ 72	$ 91