Revenue Recognition and Allowance for Credit Losses - Summary of Contract Assets and Liabilities (Details) $ in Millions	6 Months Ended
	Jun. 30, 2022 USD ($)
Accounts Receivable
Opening balance as of December 31, 2021	$ 627
Closing balance as of June 30, 2022	740
Increase (decrease) in accounts receivable	113
Other Accrued Unbilled Revenues
Opening balance as of December 31, 2021	513
Closing balance as of June 30, 2022	316
Increase (decrease) in other accrued unbilled revenues	(197)
Contract Assets
Opening balance as of December 31, 2021	15
Closing balance as of June 30, 2022	16
Increase (decrease) in contract assets	1
Contract Liabilities
Opening balance as of December 31, 2021	16
Closing balance as of June 30, 2022	39
Increase (decrease) in contract liabilities	23
Revenue recognized included in the opening contract liability for the period	13
Houston Electric
Accounts Receivable
Opening balance as of December 31, 2021	225
Closing balance as of June 30, 2022	327
Increase (decrease) in accounts receivable	102
Other Accrued Unbilled Revenues
Opening balance as of December 31, 2021	127
Closing balance as of June 30, 2022	142
Increase (decrease) in other accrued unbilled revenues	15
Contract Liabilities
Opening balance as of December 31, 2021	4
Closing balance as of June 30, 2022	6
Increase (decrease) in contract liabilities	2
Revenue recognized included in the opening contract liability for the period	2
CERC
Accounts Receivable
Opening balance as of December 31, 2021	319
Closing balance as of June 30, 2022	314
Increase (decrease) in accounts receivable	(5)
Other Accrued Unbilled Revenues
Opening balance as of December 31, 2021	335
Closing balance as of June 30, 2022	126
Increase (decrease) in other accrued unbilled revenues	$ (209)