Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019		Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Interest, net of capitalized interest			$ 364		$ 301
Income taxes, net			174		89
Accounts payable related to capital expenditures			178		140
ROU assets obtained in exchange for lease liabilities (1)			43	[1]	0
Cash and cash equivalents	$ 259		259			$ 4,231
Total cash, cash equivalents and restricted cash shown in Condensed Statements of Consolidated Cash Flows	297	$ 331	297		331	4,278	$ 296
Prepaid expenses and other current assets [Member]
Restricted cash	38		38			46
Other [Member]
Restricted cash	0		0			1
Houston Electric [Member]
Interest, net of capitalized interest			203		173
Income taxes, net			93		122
Accounts payable related to capital expenditures			91		87
ROU assets obtained in exchange for lease liabilities (1)			1	[1]	0
Cash and cash equivalents	228		228			335
Total cash, cash equivalents and restricted cash shown in Condensed Statements of Consolidated Cash Flows	247	317	247		317	370	274
Houston Electric [Member] | Prepaid expenses and other current assets [Member]
Restricted cash	19		19			34
Houston Electric [Member] | Other [Member]
Restricted cash	0		0			1
CERC Corp [Member]
Interest, net of capitalized interest			88		85
Income taxes, net			3		3
Accounts payable related to capital expenditures			75		66
Capital distribution to parent associated with the Internal Spin	0	1,460	0		1,460
ROU assets obtained in exchange for lease liabilities (1)			28	[1]	0
Cash and cash equivalents	2		2			14
Total cash, cash equivalents and restricted cash shown in Condensed Statements of Consolidated Cash Flows	2	$ 1	2		$ 1	25	$ 12
CERC Corp [Member] | Prepaid expenses and other current assets [Member]
Restricted cash	0		0			11
CERC Corp [Member] | Other [Member]
Restricted cash	$ 0		$ 0			$ 0

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