Regulatory Matters - Schedule of Allowed Equity Return Recognized (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Public Utilities, General Disclosures [Line Items]
Allowed equity return recognized	$ 40	$ 31	$ 45
Houston Electric
Public Utilities, General Disclosures [Line Items]
Allowed equity return recognized	37	31	45
CERC Corp
Public Utilities, General Disclosures [Line Items]
Allowed equity return recognized	$ 1	$ 0	$ 0