Fair Value Measurements, Including Derivatives (Schedule of Quantitative Information About Level 3 Fair Value Measurements) (Details) $ in Millions	Jun. 30, 2021 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gross assets presented in the consolidated balance sheet	$ 15
Total Liabilities, fair value	28
Electricity [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gross assets presented in the consolidated balance sheet	15
Total Liabilities, fair value	28
Minimum [Member] | Electricity [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gross assets presented in the consolidated balance sheet	23
Total Liabilities, fair value	23
Maximum [Member] | Electricity [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gross assets presented in the consolidated balance sheet	54
Total Liabilities, fair value	55
Weighted Average [Member] | Electricity [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Gross assets presented in the consolidated balance sheet	35
Total Liabilities, fair value	$ 35