STATEMENTS OF CONSOLIDATED CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows from Operating Activities:
Net income	$ 368	$ 1,792	$ 432
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,243	1,036	1,126
Amortization of deferred financing costs	48	24	26
Deferred income taxes	48	(770)	213
Unrealized loss (gain) on marketable securities	22	(7)	(326)
Loss (gain) on indexed debt securities	232	(49)	413
Write-down of natural gas inventory	2	0	1
Equity in earnings of unconsolidated affiliates, net of distributions	(40)	(265)	(208)
Pension contributions	(69)	(48)	(9)
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	(154)	(216)	(117)
Inventory	1	(7)	34
Taxes receivable	0	30	142
Accounts payable	220	136	133
Fuel cost recovery	33	(85)	(72)
Non-trading derivatives, net	103	(84)	30
Margin deposits, net	5	(55)	101
Interest and taxes accrued	40	5	5
Net regulatory assets and liabilities	28	(107)	(60)
Other current assets	0	(3)	(25)
Other current liabilities	(24)	34	22
Other assets	6	(4)	(16)
Other liabilities	12	36	30
Other, net	12	24	48
Net cash provided by operating activities	2,136	1,417	1,923
Cash Flows from Investing Activities:
Capital expenditures	(1,651)	(1,426)	(1,414)
Acquisitions, net of cash acquired	0	(132)	(102)
Decrease in notes receivable - unconsolidated affiliate	0	0	363
Investment in preferred units - unconsolidated affiliate	0	0	(363)
Distributions from unconsolidated affiliates in excess of cumulative earnings	30	297	297
Proceeds from sale of marketable securities	398	0	178
Other, net	16	4	7
Net cash provided by (used in) investing activities	(1,207)	(1,257)	(1,034)
Cash Flows from Financing Activities:
Increase (decrease) in short-term borrowings, net	(39)	4	(5)
Proceeds from (payments of) commercial paper, net	(1,543)	349	469
Proceeds from long-term debt, net	2,495	1,096	600
Payments of long-term debt	(484)	(1,211)	(1,218)
Loss on reacquired debt	0	(5)	(22)
Debt and equity issuance costs	(47)	(13)	(9)
Payment of dividends on Common Stock	(499)	(461)	(443)
Payment of dividends on preferred stock	(11)	0	0
Proceeds from issuance of Common Stock, net	1,844	0	0
Proceeds from issuance of preferred stock, net	1,740	0	0
Distribution to ZENS holders	(398)	0	(178)
Other, net	(5)	(4)	(2)
Net cash provided by (used in) financing activities	3,053	(245)	(808)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	3,982	(85)	81
Cash, Cash Equivalents and Restricted Cash at Beginning of Year	296	381	300
Cash, Cash Equivalents and Restricted Cash at End of Year	4,278	296	381
Houston Electric [Member]
Cash Flows from Operating Activities:
Net income	336	433	276
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	917	724	838
Amortization of deferred financing costs	11	13	14
Deferred income taxes	(38)	(98)	(34)
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	11	(73)	(1)
Accounts receivable/payable–affiliated companies	20	(46)	63
Inventory	(16)	15	(1)
Taxes receivable	(5)	6	53
Accounts payable	(1)	59	(4)
Non-trading derivatives, net	5	0	0
Interest and taxes accrued	(2)	7	4
Net regulatory assets and liabilities	(97)	(148)	(110)
Other current assets	(2)	(6)	(6)
Other current liabilities	(26)	16	21
Other assets	(3)	13	(8)
Other liabilities	17	(4)	(4)
Other, net	(12)	(6)	1
Net cash provided by operating activities	1,115	905	1,102
Cash Flows from Investing Activities:
Capital expenditures	(922)	(875)	(862)
Increase in notes receivable–affiliated companies	0	96	(96)
Other, net	11	3	7
Net cash provided by (used in) investing activities	(911)	(776)	(951)
Cash Flows from Financing Activities:
Proceeds from long-term debt, net	398	298	600
Payments of long-term debt	(434)	(411)	(590)
Dividend to parent	(209)	(180)	(135)
Increase (decrease) in notes payable–affiliated companies	(59)	60	(312)
Debt issuance costs	(4)	(3)	(6)
Contribution from parent	200	0	374
Net cash provided by (used in) financing activities	(108)	(236)	(69)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	96	(107)	82
Cash, Cash Equivalents and Restricted Cash at Beginning of Year	274	381	299
Cash, Cash Equivalents and Restricted Cash at End of Year	370	274	381
CERC Corp [Member]
Cash Flows from Operating Activities:
Net income	208	745	245
Income (loss) from discontinued operations, net of tax	138	161	127
Income (loss) from continuing operations	70	584	118
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	293	279	249
Amortization of deferred financing costs	9	9	9
Deferred income taxes	31	(224)	56
Write-down of natural gas inventory	2	0	1
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	(155)	(143)	(122)
Accounts receivable/payable–affiliated companies	9	0	4
Inventory	17	(22)	34
Accounts payable	163	64	117
Fuel cost recovery	33	(85)	(72)
Non-trading derivatives, net	98	(82)	29
Margin deposits, net	5	(55)	101
Interest and taxes accrued	0	(41)	26
Net regulatory assets and liabilities	50	(27)	0
Other current assets	4	2	(19)
Other current liabilities	(3)	15	2
Other assets	5	(8)	(21)
Other liabilities	6	6	(2)
Other, net	1	6	2
Net cash provided by operating activities from continuing operations	638	278	512
Net cash provided by operating activities from discontinued operations	176	0	0
Net cash provided by operating activities	814	278	512
Cash Flows from Investing Activities:
Capital expenditures	(633)	(513)	(517)
Acquisitions, net of cash acquired	0	(132)	(102)
Increase in notes receivable–affiliated companies	(114)	0	0
Other, net	3	2	1
Net cash used in investing activities from continuing operations	(744)	(643)	(618)
Net cash provided by investing activities from discontinued operations	47	297	660
Net cash provided by (used in) investing activities	(697)	(346)	42
Cash Flows from Financing Activities:
Increase (decrease) in short-term borrowings, net	(39)	4	(5)
Proceeds from (payments of) commercial paper, net	(688)	329	350
Proceeds from long-term debt, net	599	298	0
Payments of long-term debt	0	(550)	(325)
Dividend to parent	(360)	(601)	(643)
Increase (decrease) in notes payable–affiliated companies	(570)	570	0
Loss on reacquired debt	0	(5)	0
Debt issuance costs	(5)	(4)	0
Contribution from parent	960	38	72
Other, net	(1)	0	(2)
Net cash used in financing activities from continuing operations	(104)	79	(553)
Net cash provided by financing activities from discontinued operations	0	0	0
Net cash provided by (used in) financing activities	(104)	79	(553)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	13	11	1
Cash, Cash Equivalents and Restricted Cash at Beginning of Year	12	1	0
Cash, Cash Equivalents and Restricted Cash at End of Year	$ 25	$ 12	$ 1