Fair Value of Financial Instruments Financial Assets and Liabilities Recognized at Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Assets:
Cash equivalents	$ 0	$ 44
Debt securities:
Domestic government	17	19
Corporate credit	11	14
Money market funds measured at NAV (2)	11	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	41	17
Natural gas	233	120
Total	11	14
Assets, Fair Value Disclosure	320	237
Liabilities from price risk management activities: (1) (3)
Electricity	113	123
Natural gas	17	14
Total	130	137
Fair Value, Inputs, Level 1 [Member]
Assets:
Cash equivalents	0	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	16	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	11	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	25	16
Natural gas	205	115
Total	249	155
Liabilities from price risk management activities: (1) (3)
Electricity	44	33
Natural gas	12	13
Total	56	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	16	1
Natural gas	28	5
Total	44	6
Liabilities from price risk management activities: (1) (3)
Electricity	69	90
Natural gas	5	1
Total	$ 74	$ 91