Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest, net of capitalized interest	$ 471	$ 436	$ 363
Income taxes (refunds), net	143	155	89
Accounts payable related to capital expenditures	153	236	201
Capital distribution to parent associated with the sale of CES	0	0	0
ROU Asset Obtained In Exchange for Operating Lease Liability, Including Transition Impact of ASC 842 Adoption	15	44	0
Beneficial Conversion Feature	32	0	0
Amortization of Beneficial Conversion Feature	(32)	0	0
Cash and cash equivalents	147	241
Total cash, cash equivalents and restricted cash shown in Statements of Consolidated Cash Flows	167	271	4,278	$ 296
Prepaid Expenses and Other Current Assets [Member]
Restricted cash	20	30
Houston Electric [Member]
Interest, net of capitalized interest	201	229	200
Income taxes (refunds), net	65	87	154
Accounts payable related to capital expenditures	102	117	124
Capital distribution to parent associated with the sale of CES	0	0	0
ROU Asset Obtained In Exchange for Operating Lease Liability, Including Transition Impact of ASC 842 Adoption	1	1	0
Beneficial Conversion Feature	0	0	0
Amortization of Beneficial Conversion Feature	0	0	0
Cash and cash equivalents	139	216
Total cash, cash equivalents and restricted cash shown in Statements of Consolidated Cash Flows	154	235	370	274
Houston Electric [Member] | Prepaid Expenses and Other Current Assets [Member]
Restricted cash	15	19
CERC Corp [Member]
Interest, net of capitalized interest	114	109	105
Income taxes (refunds), net	4	7	3
Accounts payable related to capital expenditures	69	86	80
Capital distribution to parent associated with the sale of CES	0	28	1,473
ROU Asset Obtained In Exchange for Operating Lease Liability, Including Transition Impact of ASC 842 Adoption	5	29	0
Beneficial Conversion Feature	0	0	0
Amortization of Beneficial Conversion Feature	0	0	0
Cash and cash equivalents	1	2
Total cash, cash equivalents and restricted cash shown in Statements of Consolidated Cash Flows	1	2	$ 25	$ 12
CERC Corp [Member] | Prepaid Expenses and Other Current Assets [Member]
Restricted cash	0	0
Bond Companies [Member] | Houston Electric [Member]
Cash and cash equivalents	$ 139	$ 216