Fair Value of Financial Instruments Financial Assets and Liabilities Recognized at Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Assets:
Cash equivalents	$ 41	$ 12
Debt securities:
Domestic government	25	16
Corporate credit	10	7
Money market funds measured at NAV (2)	7	7
Non-qualified benefit plan trust: (2)
Alternative Investment	6	4
Debt securities—domestic government	1	2
Assets from price risk management activities: (1) (3)
Electricity	13	19
Natural gas	20	15
Total	13	11
Assets, Fair Value Disclosure	123	82
Liabilities from price risk management activities: (1) (3)
Electricity	48	56
Natural gas	107	163
Total	155	219
Fair Value, Inputs, Level 1 [Member]
Assets:
Cash equivalents	41	12
Debt securities:
Domestic government	14	10
Corporate credit	0	0
Non-qualified benefit plan trust: (2)
Debt securities—domestic government	1	2
Assets from price risk management activities: (1) (3)
Electricity	0	0
Natural gas	0	0
Total	56	24
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	11	6
Corporate credit	10	7
Non-qualified benefit plan trust: (2)
Debt securities—domestic government	0	0
Assets from price risk management activities: (1) (3)
Electricity	9	18
Natural gas	19	15
Total	49	46
Liabilities from price risk management activities: (1) (3)
Electricity	17	25
Natural gas	102	159
Total	119	184
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)
Debt securities—domestic government	0	0
Assets from price risk management activities: (1) (3)
Electricity	4	1
Natural gas	1	0
Total	5	1
Liabilities from price risk management activities: (1) (3)
Electricity	31	31
Natural gas	5	4
Total	$ 36	$ 35