Short-term Borrowings and Long-term Debt - Debt Transactions (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($)
General Mortgage Bonds | Houston Electric
Debt Instrument [Line Items]
Principal amount of debt issued	$ 800
Proceeds from issuance of long-term debt, net of discounts and issuance expenses and fees	784
Senior Note and GMBs
Debt Instrument [Line Items]
Principal amount of debt issued	800
General Mortgage Bonds Due 2031 | General Mortgage Bonds | Houston Electric
Debt Instrument [Line Items]
Principal amount of debt issued	$ 300
Interest rate of debt (as a percent)	3.00%
General Mortgage Bonds Due 2051 | General Mortgage Bonds | Houston Electric
Debt Instrument [Line Items]
Principal amount of debt issued	$ 500
Interest rate of debt (as a percent)	3.60%