Short-term Borrowings and Long-term Debt - Schedule of Utilization of Credit Facilities (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Revolving Credit Facility
Debt Instrument [Line Items]
Long-term line of credit	$ 0	$ 0
Revolving Credit Facility | VUHI
Debt Instrument [Line Items]
Long-term line of credit	0	0
Revolving Credit Facility | CenterPoint Energy
Debt Instrument [Line Items]
Long-term line of credit	0	0
Revolving Credit Facility | Houston Electric
Debt Instrument [Line Items]
Long-term line of credit	0	0
Revolving Credit Facility | CERC Corp
Debt Instrument [Line Items]
Long-term line of credit	0	0
Letter of Credit
Debt Instrument [Line Items]
Long-term line of credit	11	11
Letter of Credit | VUHI
Debt Instrument [Line Items]
Long-term line of credit	0	0
Letter of Credit | CenterPoint Energy
Debt Instrument [Line Items]
Long-term line of credit	11	11
Letter of Credit | Houston Electric
Debt Instrument [Line Items]
Long-term line of credit	0	0
Letter of Credit | CERC Corp
Debt Instrument [Line Items]
Long-term line of credit	0	0
Commercial Paper
Debt Instrument [Line Items]
Long-term line of credit	1,743	1,517
Commercial Paper | VUHI
Debt Instrument [Line Items]
Long-term line of credit	$ 268	$ 92
Weighted average interest rate of debt (as a percent)	0.18%	0.22%
Commercial Paper | CenterPoint Energy
Debt Instrument [Line Items]
Long-term line of credit	$ 911	$ 1,078
Weighted average interest rate of debt (as a percent)	0.18%	0.23%
Number of days until commercial paper maturity	60 days
Commercial Paper | Houston Electric
Debt Instrument [Line Items]
Long-term line of credit	$ 0	$ 0
Weighted average interest rate of debt (as a percent)	0.00%	0.00%
Commercial Paper | CERC Corp
Debt Instrument [Line Items]
Long-term line of credit	$ 564	$ 347
Weighted average interest rate of debt (as a percent)	0.18%	0.23%