Fair Value Measurements, Including Derivatives (Schedule of Quantitative Information About Level 3 Fair Value Measurements) (Details)	Sep. 30, 2023 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets, fair value	$ 171,000,000
Electricity [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets, fair value	171,000,000
Minimum [Member] | Electricity [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets, fair value	25,000,000
Maximum [Member] | Electricity [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets, fair value	92,000,000
Weighted Average [Member] | Electricity [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets, fair value	$ 48,000,000	[1]

[1] Averages weighted by volume.