Significant Accounting Policies (Intangible Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	$ (119)	$ (103)
Indefinite-lived Intangible Assets [Line Items]
Intangible assets not subject to amortization	17	13
Long-term intangible assets
Gross Carrying Value	263	259
Accumulated Amortization	(119)	(103)
Net Carrying Value	144	156
Carbon offsets
Indefinite-lived Intangible Assets [Line Items]
Intangible assets not subject to amortization	14	10
Renewable energy credits
Indefinite-lived Intangible Assets [Line Items]
Intangible assets not subject to amortization	1	2
Other
Indefinite-lived Intangible Assets [Line Items]
Intangible assets not subject to amortization	2	1
Contract intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	246	246
Accumulated Amortization	(119)	(103)
Net Carrying Value	127	143
Long-term intangible assets
Accumulated Amortization	$ (119)	$ (103)
Contract intangibles | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Lives	12 years
Contract intangibles | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Lives	26 years