Debt (Narrative) (Details) - Letters Of Credit, Due 2026 [Member]	9 Months Ended
	Sep. 30, 2021 USD ($)
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 2,500,000,000
Minimum consolidated net worth	$ 10,000,000,000.0
Percentage of aggregate net proceeds of equity issuances	50.00%
Debt to capital ratio (low end of range)	0.35%
Debt to capital ratio (high end of range)	1.00%
Non-operating indebtedness of subsidiaries to total capitalization, maximum	7.50%