Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019		Dec. 31, 2019	Dec. 31, 2018
Interest, net of capitalized interest	$ 148	$ 154
Income tax refunds, net	0	(4)
Accounts payable related to capital expenditures	200	166
ROU assets obtained in exchange for lease liabilities (1)	14	29	[1]
Cash and cash equivalents	220			$ 241
Total cash, cash equivalents and restricted cash shown in Condensed Statements of Consolidated Cash Flows	247	355		271	$ 4,278
Prepaid expenses and other current assets [Member]
Restricted cash	27			30
Houston Electric [Member]
Interest, net of capitalized interest	68	86
Income tax refunds, net	0	0
Accounts payable related to capital expenditures	110	98
ROU assets obtained in exchange for lease liabilities (1)	0	1	[1]
Cash and cash equivalents	196			216
Total cash, cash equivalents and restricted cash shown in Condensed Statements of Consolidated Cash Flows	215	277		235	370
Houston Electric [Member] | Prepaid expenses and other current assets [Member]
Restricted cash	19			19
CERC Corp [Member]
Interest, net of capitalized interest	35	35
Income tax refunds, net	0	0
Accounts payable related to capital expenditures	66	49
ROU assets obtained in exchange for lease liabilities (1)	5	26	[1]
Cash and cash equivalents	1			2
Total cash, cash equivalents and restricted cash shown in Condensed Statements of Consolidated Cash Flows	1	$ 12		2	$ 25
CERC Corp [Member] | Prepaid expenses and other current assets [Member]
Restricted cash	$ 0			$ 0

[1] 2019 includes the transition impact of adoption of ASU 2016-02 Leases.