Revenue Recognition - Summary of Contract Assets and Liabilities (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($)
Accounts Receivable
Opening balance as of December 31, 2020	$ 604
Closing balance as of December 31, 2021	627
Increase (Decrease) in Accounts Receivable	23
Other Accrued Unbilled Revenues
Opening balance as of December 31, 2020	505
Closing balance as of December 31, 2021	513
Increase (Decrease) in Other Accrued Unbilled Revenues	8
Contract Assets
Opening balance as of December 31, 2020	27
Closing balance as of December 31, 2021	15
Increase (Decrease) in Contract with Customer, Asset	(12)
Contract Liabilities
Opening balance as of December 31, 2020	18
Closing balance as of December 31, 2021	16
Increase (Decrease) in Contract with Customer, Liability	(2)
Revenue recognized included in the opening contract liability for the period	17
Houston Electric
Accounts Receivable
Opening balance as of December 31, 2020	225
Closing balance as of December 31, 2021	225
Increase (Decrease) in Accounts Receivable	0
Other Accrued Unbilled Revenues
Opening balance as of December 31, 2020	113
Closing balance as of December 31, 2021	127
Increase (Decrease) in Other Accrued Unbilled Revenues	14
Contract Liabilities
Opening balance as of December 31, 2020	3
Closing balance as of December 31, 2021	4
Increase (Decrease) in Contract with Customer, Liability	1
Revenue recognized included in the opening contract liability for the period	3
CERC Corp
Accounts Receivable
Opening balance as of December 31, 2020	214
Closing balance as of December 31, 2021	223
Increase (Decrease) in Accounts Receivable	9
Other Accrued Unbilled Revenues
Opening balance as of December 31, 2020	261
Closing balance as of December 31, 2021	247
Increase (Decrease) in Other Accrued Unbilled Revenues	$ (14)