Significant Accounting Policies (Intangible Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	$ (103)	$ (88)
Indefinite-lived Intangible Assets [Line Items]
Intangible assets not subject to amortization	13	8
Long-term intangible assets
Gross Carrying Value	259	254
Accumulated Amortization	(103)	(88)
Net Carrying Value	156	166
Carbon offsets
Indefinite-lived Intangible Assets [Line Items]
Intangible assets not subject to amortization	10	6
Renewable energy credits
Indefinite-lived Intangible Assets [Line Items]
Intangible assets not subject to amortization	2	2
Other
Indefinite-lived Intangible Assets [Line Items]
Intangible assets not subject to amortization	1	0
Contract intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	246	246
Accumulated Amortization	(103)	(88)
Net Carrying Value	143	158
Long-term intangible assets
Accumulated Amortization	$ (103)	$ (88)
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