Long-term Debt Schedule of Long Term Debt Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Mar. 11, 2020
Debt Instrument [Line Items]
First mortgage Bonds - minimum rate	1.82%
First Mortgage Bonds, rates range from 2.51% to 9.31%, with a weighted average rate of 4.63% in 2019 and 5.01% in 2018, due at various dates through 2050	$ 3,180	$ 2,940
Pollution Control Revenue Bonds, 5% rate, due 2033	119	119	$ 119
Total long-term debt	3,299	3,059
Debt Instrument, Unamortized Discount	(14)	(13)
Less: current portion of long-term debt	0	(160)
Long-term debt, net of current portion	$ 3,285	$ 2,886
First Mortgage Bonds - maximum rate	6.88%
Debt, Weighted Average Interest Rate	4.11%	4.14%