Related Party Transactions (Houston Electric and CERC) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Related Party Transaction [Line Items]
Total Assets	$ 36,216		$ 36,216		$ 37,679
Retained earnings	768		768		154
Total shareholders’ equity	10,023	$ 8,870	10,023	$ 8,870	9,415
Net income	190	251	721	614
Houston Electric
Related Party Transaction [Line Items]
Cash dividends paid to parent	30	0	67	0
Cash dividend paid to parent related to the sale of the Arkansas and Oklahoma Natural Gas businesses	0	0	0	0
Cash contribution from parent	506	0	1,143	0
Net assets acquired in the Restructuring	0	0	0	0
Non-cash capital contribution from parent in payment for property, plant and equipment below	0	0	38	0
Cash paid to parent for property, plant and equipment below	13	0	65	0
Property, plant and equipment from parent	13	0	103	0
Total Assets	14,306		14,306		12,980
Retained earnings	1,085		1,085		944
Total shareholders’ equity	4,945	3,267	4,945	3,267	3,622
Net income	147	103	208	156
Houston Electric | Operation and maintenance expense
Related Party Transaction [Line Items]
Net affiliate service charges (billings)	(9)	(1)	(15)	(2)
Houston Electric | CenterPoint Energy | Operation and maintenance expense
Related Party Transaction [Line Items]
Corporate service charges	37	47	76	90
CERC
Related Party Transaction [Line Items]
Cash dividends paid to parent	72	0	111	0
Cash dividend paid to parent related to the sale of the Arkansas and Oklahoma Natural Gas businesses	0	0	720	0
Cash contribution from parent	125	0	125	0
Net assets acquired in the Restructuring	2,345	0	2,345	0
Non-cash capital contribution from parent in payment for property, plant and equipment below	0	0	54	0
Cash paid to parent for property, plant and equipment below	13	0	61	0
Property, plant and equipment from parent	13	0	115	0
Total Assets	14,278		14,278		16,153
Liabilities					11,020
Retained earnings	1,569		1,569		1,017
Total shareholders’ equity	5,144	4,914	5,144	4,914	5,133
Net income	27	73	663	295
CERC | Previously Reported
Related Party Transaction [Line Items]
Total Assets					11,110
Liabilities					8,109
Retained earnings					765
Total shareholders’ equity					3,001
Net income		58		209
CERC | Operation and maintenance expense
Related Party Transaction [Line Items]
Net affiliate service charges (billings)	9	1	15	2
CERC | CenterPoint Energy | Operation and maintenance expense
Related Party Transaction [Line Items]
Corporate service charges	$ 51	$ 58	$ 109	$ 114
IGC and VEDO
Related Party Transaction [Line Items]
Notes Payable, Related Parties					$ 217
Weighted average interest rate of debt (as a percent)					0.21%
Investments | Houston Electric
Related Party Transaction [Line Items]
Money pool weighted average interest rate (as a percent)	1.85%		1.85%		0.34%
Investments | CERC
Related Party Transaction [Line Items]
Money pool weighted average interest rate (as a percent)	1.85%		1.85%		0.34%
Accounts and notes receivable (payable) - affiliate companies | Houston Electric
Related Party Transaction [Line Items]
Money pool investments (borrowings)	$ 272		$ 272		$ (512)
Accounts and notes receivable (payable) - affiliate companies | CERC
Related Party Transaction [Line Items]
Money pool investments (borrowings)	$ 0		$ 0		$ (224)