Condensed Consolidated Balance Sheets - CERC (Parenthetical) - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Cash and cash equivalents	$ 125,000,000	$ 230,000,000
Accounts receivable, less allowance for credit losses	943,000,000	690,000,000
Allowance for credit losses	39,000,000	44,000,000
Accrued unbilled revenues, allowance for credit losses	2,000,000	6,000,000
Prepaid expenses and other current assets	100,000,000	132,000,000
Regulatory assets	$ 2,270,000,000	$ 2,321,000,000
Preferred Stock [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	20,000,000	20,000,000
Preferred stock, outstanding (in shares)	800,000	800,000
Preferred stock aggregate liquidation preference	$ 800	$ 800
Common Stock [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	1,000,000,000	1,000,000,000
Common stock, outstanding (in shares)	629,432,406	628,923,534
CERC Corp
Cash and cash equivalents	$ 4,000,000	$ 8,000,000
Accounts receivable, less allowance for credit losses	426,000,000	240,000,000
Allowance for credit losses	33,000,000	39,000,000
Accrued unbilled revenues, allowance for credit losses	2,000,000	5,000,000
Prepaid expenses and other current assets	13,000,000	15,000,000
Regulatory assets	534,000,000	577,000,000
Variable Interest Entity, Primary Beneficiary
Cash and cash equivalents	104,000,000	92,000,000
Accounts receivable, less allowance for credit losses	29,000,000	29,000,000
Prepaid expenses and other current assets	18,000,000	19,000,000
Regulatory assets	$ 372,000,000	$ 420,000,000