CONDENSED STATEMENTS OF CONSOLIDATED CASH FLOW (Unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash Flows from Operating Activities:
Net income	$ 90	$ 327
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	656	480
Amortization of deferred financing costs	18	12
Deferred income taxes	(12)	95
Unrealized gain on marketable securities	(23)	(67)
Loss on indexed debt securities	272	23
Write-down of natural gas inventory	1	0
Equity in earnings of unconsolidated affiliate, net of distributions	(9)	(131)
Pension contributions	(64)	(18)
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	232	234
Inventory	52	(20)
Taxes receivable	(39)	30
Accounts payable	(246)	(158)
Fuel cost recovery	69	(12)
Non-trading derivatives, net	64	(49)
Margin deposits, net	(9)	(43)
Interest and taxes accrued	(64)	(17)
Net regulatory assets and liabilities	57	(34)
Other current assets	(4)	10
Other current liabilities	(13)	(29)
Other assets	(3)	(1)
Other liabilities	60	27
Other, net	8	18
Net cash provided by operating activities	1,093	677
Cash Flows from Investing Activities:
Capital expenditures	(697)	(649)
Acquisitions, net of cash acquired	0	(132)
Distributions from unconsolidated affiliate in excess of cumulative earnings	30	149
Proceeds from sale of marketable securities	398	0
Other, net	2	(8)
Net cash used in investing activities	(267)	(640)
Cash Flows from Financing Activities:
Decrease in short-term borrowings, net	(39)	(11)
Proceeds from (payments of) commercial paper, net	(1,188)	284
Proceeds from long-term debt, net	997	298
Payments of long-term debt	(230)	(469)
Debt issuance costs	(35)	(6)
Payment of dividends on common stock	(240)	(230)
Distribution to ZENS note holders	(16)	0
Other, net	(5)	(4)
Net cash provided by (used in) financing activities	(756)	(138)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	70	(101)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	296	381
Cash, Cash Equivalents and Restricted Cash at End of Period	366	280
Cash and Cash Equivalents at Beginning of Period	260
Cash and Cash Equivalents at End of Period	328
Houston Electric [Member]
Cash Flows from Operating Activities:
Net income	153	93
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	495	332
Amortization of deferred financing costs	6	6
Deferred income taxes	(38)	23
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	(107)	(63)
Accounts receivable/payable–affiliated companies	78	(35)
Inventory	(6)	(1)
Taxes receivable	(23)	(38)
Accounts payable	(6)	57
Interest and taxes accrued	(45)	(41)
Net regulatory assets and liabilities	(59)	(59)
Other current assets	4	2
Other current liabilities	(11)	(7)
Other assets	2	4
Other liabilities	2	1
Other, net	(2)	5
Net cash provided by operating activities	443	279
Cash Flows from Investing Activities:
Capital expenditures	(441)	(414)
Decrease (increase) in notes receivable–affiliated companies	(26)	5
Other, net	(1)	(9)
Net cash used in investing activities	(468)	(418)
Cash Flows from Financing Activities:
Proceeds from long-term debt, net	398	298
Payments of long-term debt	(230)	(219)
Decrease in notes payable–affiliated companies	(60)	0
Dividend to parent	(63)	(42)
Debt issuance costs	(4)	(3)
Other, net	1	1
Net cash provided by (used in) financing activities	42	35
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	17	(104)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	274	381
Cash, Cash Equivalents and Restricted Cash at End of Period	291	277
Cash and Cash Equivalents at Beginning of Period	238
Cash and Cash Equivalents at End of Period	253
CERC Corp [Member]
Cash Flows from Operating Activities:
Net income	166	201
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	145	134
Amortization of deferred financing costs	4	4
Deferred income taxes	41	115
Write-down of natural gas inventory	1	0
Equity in earnings of unconsolidated affiliate, net of distributions	(9)	(131)
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	339	295
Accounts receivable/payable–affiliated companies	(14)	(1)
Inventory	58	(18)
Accounts payable	(248)	(203)
Fuel cost recovery	69	(12)
Non-trading derivatives, net	61	(49)
Margin deposits, net	(9)	(43)
Interest and taxes accrued	(21)	(27)
Net regulatory assets and liabilities	92	(1)
Other current assets	7	12
Other current liabilities	8	(14)
Other assets	4	5
Other liabilities	52	10
Other, net	0	1
Net cash provided by operating activities	746	278
Cash Flows from Investing Activities:
Capital expenditures	(230)	(223)
Acquisitions, net of cash acquired	0	(132)
Distributions from unconsolidated affiliate in excess of cumulative earnings	30	149
Other, net	3	1
Net cash used in investing activities	(197)	(205)
Cash Flows from Financing Activities:
Decrease in short-term borrowings, net	(39)	(11)
Proceeds from (payments of) commercial paper, net	(333)	149
Proceeds from long-term debt, net	599	0
Decrease in notes payable–affiliated companies	(570)	0
Dividend to parent	(211)	(248)
Debt issuance costs	(5)	(1)
Contribution from parent	0	38
Other, net	(1)	0
Net cash provided by (used in) financing activities	(560)	(73)
Net Decrease in Cash and Cash Equivalents	(11)	0
Cash and Cash Equivalents at Beginning of Period	12	1
Cash and Cash Equivalents at End of Period	$ 1	$ 1