Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019		Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Interest, net of capitalized interest	$ 231		$ 167
Income taxes (refunds), net	142		88
Accounts payable related to capital expenditures	173		133
ROU assets obtained in exchange for lease liabilities (1)	42	[1]	0
Cash and cash equivalents	271			$ 4,231
Total cash, cash equivalents and restricted cash shown in Condensed Statements of Consolidated Cash Flows	332		366	4,278	$ 296
Prepaid expenses and other current assets [Member]
Restricted cash	61			46
Other [Member]
Restricted cash	0			1
Houston Electric [Member]
Interest, net of capitalized interest	113		90
Income taxes (refunds), net	73		120
Accounts payable related to capital expenditures	86		75
ROU assets obtained in exchange for lease liabilities (1)	1	[1]	0
Cash and cash equivalents	260			335
Total cash, cash equivalents and restricted cash shown in Condensed Statements of Consolidated Cash Flows	293		291	370	274
Houston Electric [Member] | Prepaid expenses and other current assets [Member]
Restricted cash	33			34
Houston Electric [Member] | Other [Member]
Restricted cash	0			1
CERC Corp [Member]
Interest, net of capitalized interest	55		50
Income taxes (refunds), net	3		3
Accounts payable related to capital expenditures	72		69
ROU assets obtained in exchange for lease liabilities (1)	28	[1]	0
Cash and cash equivalents	1			14
Total cash, cash equivalents and restricted cash shown in Condensed Statements of Consolidated Cash Flows	5		$ 1	25	$ 12
CERC Corp [Member] | Prepaid expenses and other current assets [Member]
Restricted cash	4			11
CERC Corp [Member] | Other [Member]
Restricted cash	$ 0			$ 0

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