Reportable Segments Revenues by Products and Services (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) state	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Segment Reporting Information [Line Items]
Operating revenues	$ 7,418	$ 7,564	$ 6,277
CenterPoint Energy [Member]
Segment Reporting Information [Line Items]
Operating revenues	7,418	7,564	6,277
CenterPoint Energy [Member] | Electric Delivery [Member]
Segment Reporting Information [Line Items]
Operating revenues	2,941	3,019	3,232
CenterPoint Energy [Member] | Retail Electric Sales [Member]
Segment Reporting Information [Line Items]
Operating revenues	515	486
CenterPoint Energy [Member] | Wholesale Electric Sales [Member]
Segment Reporting Information [Line Items]
Operating revenues	14	14
CenterPoint Energy [Member] | Retail Gas Sales [Member]
Segment Reporting Information [Line Items]
Operating revenues	3,462	3,563	2,857
CenterPoint Energy [Member] | Gas Transportation and Processing [Member]
Segment Reporting Information [Line Items]
Operating revenues	15	33	32
CenterPoint Energy [Member] | Energy Products and Services [Member]
Segment Reporting Information [Line Items]
Operating revenues	471	449	156
Houston Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	2,911	2,990	3,234
Houston Electric [Member] | Electric Delivery [Member]
Segment Reporting Information [Line Items]
Operating revenues	2,911	2,990	3,234
Houston Electric [Member] | Retail Gas Sales [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0	0
Houston Electric [Member] | Gas Transportation and Processing [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0	0
Houston Electric [Member] | Energy Products and Services [Member]
Segment Reporting Information [Line Items]
Operating revenues	0	0	0
CERC Corp [Member]
Segment Reporting Information [Line Items]
Operating revenues	$ 2,763	3,018	3,031
CERC Corp [Member] | Natural Gas Distribution
Segment Reporting Information [Line Items]
Number of States in which the Entity Performs Gas Delivery Services | state	48
CERC Corp [Member] | Electric Delivery [Member]
Segment Reporting Information [Line Items]
Operating revenues	$ 0	0	0
CERC Corp [Member] | Retail Gas Sales [Member]
Segment Reporting Information [Line Items]
Operating revenues	2,594	2,831	2,857
CERC Corp [Member] | Gas Transportation and Processing [Member]
Segment Reporting Information [Line Items]
Operating revenues	15	33	32
CERC Corp [Member] | Energy Products and Services [Member]
Segment Reporting Information [Line Items]
Operating revenues	$ 154	$ 154	$ 142