Divestitures (CenterPoint Energy and CERC) - Financial Information and Pro Forma (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total revenues	$ 7,418	$ 7,564	$ 6,277
Net income (loss)	$ (773)	791	368
Vectren [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total revenues		2,729
Net income (loss)		190
Operating Revenue		12,547	13,282
Net Income (1)		812	458
Vectren acquisition [Member] | Pro Forma [Member] | Vectren [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Transaction costs associated with the Merger		$ 37	$ 37