Borrowings and Other Financing Instruments Term Loan (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Short-term Debt [Line Items]
Amount outstanding at period end	$ 0		$ 813
Proceeds from issuance of common stock	83	$ 156
Letter of Credit
Short-term Debt [Line Items]
Amount outstanding at period end	$ 46		$ 43