STATEMENTS OF CONSOLIDATED CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Flows from Operating Activities:
Net Income (Loss)	$ (773)	$ 791	$ 368
Net income (loss) from Discontinued Operations	(182)	109	(28)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,189	1,225	1,230
Depreciation and amortization on assets held for sale	0	62	13
Amortization of deferred financing costs	28	29	48
Deferred income taxes	(429)	69	48
Amortization of intangible assets in Non-utility cost of revenues	2	24	0
Goodwill impairment and loss from reclassification to held for sale	175	48	0
Goodwill impairment	185	0	0
Loss on early extinguishment of debt	2	0	0
Unrealized loss (gain) on marketable securities	(49)	(282)	22
Loss (gain) on indexed debt securities	60	292	232
Write-down of natural gas inventory	3	4	2
Equity in earnings of unconsolidated affiliates	1,428	(230)	(307)
Distributions from unconsolidated affiliates	113	261	267
Pension contributions	(86)	(109)	(69)
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	90	226	(154)
Inventory	9	(52)	1
Taxes receivable	24	(106)	0
Accounts payable	2	(455)	220
Fuel cost recovery	(21)	92	33
Non-trading derivatives, net	0	(64)	103
Margin deposits, net	72	(56)	5
Interest and taxes accrued	24	54	40
Net regulatory assets and liabilities	(86)	(114)	28
Other current assets	(20)	(22)	0
Other current liabilities	28	(107)	(24)
Other assets	12	103	6
Other liabilities	13	(54)	12
Other, net	0	9	12
Net cash provided by operating activities	1,995	1,638	2,136
Cash Flows from Investing Activities:
Capital expenditures	(2,596)	(2,506)	(1,651)
Acquisitions, net of cash acquired	0	(5,991)	0
Distributions from unconsolidated affiliates in excess of cumulative earnings	80	42	30
Proceeds from sale of marketable securities	0	0	398
Proceeds from divestitures (Note 4)	1,215	0	0
Proceeds from sale of assets	0	5	0
Purchase of investments	0	(6)	0
Other, net	36	35	16
Net Cash Provided by (Used in) Investing Activities	(1,265)	(8,421)	(1,207)
Cash Flows from Financing Activities:
Decrease in short-term borrowings, net	0	0	(39)
Proceeds from Lines of Credit	1,050	135	0
Repayments of Lines of Credit	(1,050)	(135)	0
Proceeds from (payments of) commercial paper, net	(761)	1,891	(1,543)
Proceeds from long-term debt	799	2,916	2,495
Payments of long-term debt	(1,724)	(1,302)	(484)
Payment of debt issuance costs	(8)	(20)	(47)
Payment of dividends on Common Stock	(392)	(577)	(499)
Payment of dividends on preferred stock	(137)	(118)	(11)
Proceeds from issuance of Common Stock, net	672	0	1,844
Proceeds from Issuance of Preferred Stock and Preference Stock	723	0	1,740
Distribution to ZENS holders	0	0	(398)
Other, net	(6)	(14)	(5)
Net cash provided by (used in) financing activities	(834)	2,776	3,053
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(104)	(4,007)	3,982
Cash, Cash Equivalents and Restricted Cash at Beginning of Year	271	4,278	296
Cash, Cash Equivalents and Restricted Cash at End of Year	167	271	4,278
Houston Electric [Member]
Cash Flows from Operating Activities:
Net Income (Loss)	334	356	336
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	560	648	917
Amortization of deferred financing costs	11	12	11
Deferred income taxes	(42)	(24)	(38)
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	(26)	38	11
Accounts receivable/payable–affiliated companies	47	(23)	20
Inventory	(48)	(12)	(16)
Taxes receivable	0	5	(5)
Accounts payable	28	13	(1)
Non-trading derivatives, net	15	(25)	5
Interest and taxes accrued	43	13	(2)
Net regulatory assets and liabilities	(11)	(48)	(97)
Other current assets	(8)	(5)	(2)
Other current liabilities	5	(9)	(26)
Other assets	(7)	5	(3)
Other liabilities	11	(12)	17
Other, net	(13)	(14)	(12)
Net cash provided by operating activities	899	918	1,115
Cash Flows from Investing Activities:
Capital expenditures	(1,058)	(1,025)	(922)
(Increase) decrease in notes receivable–affiliated companies	481	(481)	0
Other, net	13	11	11
Net Cash Provided by (Used in) Investing Activities	(564)	(1,495)	(911)
Cash Flows from Financing Activities:
Proceeds from long-term debt	299	696	398
Payments of long-term debt	(231)	(458)	(434)
Dividend to parent	(551)	(376)	(209)
Increase (decrease) in notes payable–affiliated companies	8	(1)	(59)
Debt issuance costs	(3)	(8)	(4)
Contribution from parent	62	590	200
Other, net	0	(1)	0
Net cash provided by (used in) financing activities	(416)	442	(108)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(81)	(135)	96
Cash, Cash Equivalents and Restricted Cash at Beginning of Year	235	370	274
Cash, Cash Equivalents and Restricted Cash at End of Year	154	235	370
CERC Corp [Member]
Cash Flows from Operating Activities:
Net Income (Loss)	81	212	208
Net income (loss) from Discontinued Operations	(66)	23	110
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	304	293	280
Depreciation and amortization on assets held for sale	0	12	13
Amortization of deferred financing costs	8	9	9
Deferred income taxes	91	7	64
Goodwill impairment and loss from reclassification to held for sale	93	48	0
Loss on early extinguishment of debt	2	0	0
Write-down of natural gas inventory	3	4	2
Equity in earnings of unconsolidated affiliates	0	0	(184)
Distributions from unconsolidated affiliates	0	0	176
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	151	252	(155)
Accounts receivable/payable–affiliated companies	4	(6)	9
Inventory	63	(12)	17
Accounts payable	(72)	(305)	163
Fuel cost recovery	(21)	86	33
Non-trading derivatives, net	(12)	(60)	98
Margin deposits, net	65	(56)	5
Interest and taxes accrued	(15)	2	13
Net regulatory assets and liabilities	(31)	(10)	50
Other current assets	(1)	1	4
Other current liabilities	10	22	(3)
Other assets	15	5	5
Other liabilities	(1)	(38)	6
Other, net	(8)	0	1
Net cash provided by operating activities	729	466	814
Cash Flows from Investing Activities:
Capital expenditures	(815)	(776)	(633)
(Increase) decrease in notes receivable–affiliated companies	(9)	114	(114)
Distributions from unconsolidated affiliates in excess of cumulative earnings	0	0	47
Proceeds from divestitures (Note 4)	365
Other, net	7	0	3
Net Cash Provided by (Used in) Investing Activities	(452)	(662)	(697)
Cash Flows from Financing Activities:
Decrease in short-term borrowings, net	0	0	(39)
Proceeds from (payments of) commercial paper, net	(30)	167	(688)
Proceeds from long-term debt	500	0	599
Payments of long-term debt	(593)	0	0
Dividend to parent	(80)	(120)	(360)
Increase (decrease) in notes payable–affiliated companies	0	0	(570)
Debt issuance costs	(4)	0	(5)
Contribution from parent	217	129	960
Capital distribution to parent associated with the sale of CES	(286)	0	0
Other, net	(2)	(3)	(1)
Net cash provided by (used in) financing activities	(278)	173	(104)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(1)	(23)	13
Cash, Cash Equivalents and Restricted Cash at Beginning of Year	2	25	12
Cash, Cash Equivalents and Restricted Cash at End of Year	$ 1	$ 2	$ 25