CONDENSED STATEMENTS OF CONSOLIDATED CASH FLOWS (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash Flows from Operating Activities:
Net income (loss)	$ 363	$ (1,199)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	307	282
Amortization of deferred financing costs	7	7
Deferred income taxes	66	(377)
Goodwill impairment and loss from reclassification to held for sale	0	214
Goodwill Impairment	0	185
Unrealized loss on marketable securities	23	144
Gain on indexed debt securities	(26)	(135)
Write-down of natural gas inventory	0	3
Equity in (earnings) losses of unconsolidated affiliates	(108)	1,475
Distributions from unconsolidated affiliates	39	70
Pension contributions	(8)	(2)
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	29	236
Inventory	99	110
Taxes receivable	3	13
Accounts payable	(55)	(192)
Non-trading derivatives, net	(14)	(53)
Margin deposits, net	0	21
Interest and taxes accrued	(62)	(95)
Net regulatory assets and liabilities	(2,297)	(27)
Other current assets	0	(5)
Other current liabilities	(59)	(37)
Other non-current assets	0	19
Other non-current liabilities	17	1
Other, net	(5)	4
Net Cash Provided by (Used in) Operating Activities, Total	(1,681)	662
Cash Flows from Investing Activities:
Capital expenditures	(594)	(664)
Distributions from unconsolidated affiliate in excess of cumulative earnings	0	7
Other, net	(10)	3
Net Cash Provided by (Used in) Investing Activities, Total	(604)	(654)
Cash Flows from Financing Activities:
Proceeds from (payments of) commercial paper, net	38	(828)
Proceeds from long-term debt	2,795	0
Payments of long-term debt	(388)	(63)
Proceeds from Lines of Credit	0	1,050
Payment of debt issuance costs	(20)	0
Payment of dividends on Common Stock	(88)	(145)
Payment of dividends on Preferred Stock	(48)	(42)
Other, net	(4)	(4)
Net cash provided by (used in) financing activities from continuing operations	2,285	(32)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	0	(24)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	167	271
Cash, Cash Equivalents and Restricted Cash at End of Period	167	247
Houston Electric [Member]
Cash Flows from Operating Activities:
Net income (loss)	53	33
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	141	129
Amortization of deferred financing costs	3	3
Deferred income taxes	(5)	(1)
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	21	19
Accounts receivable/payable–affiliated companies	(49)	(3)
Inventory	(7)	(10)
Accounts payable	14	(2)
Interest and taxes accrued	(73)	(80)
Net regulatory assets and liabilities	(63)	(11)
Other current assets	16	13
Other current liabilities	(2)	8
Other non-current assets	3	0
Other non-current liabilities	0	8
Other, net	(5)	(3)
Net Cash Provided by (Used in) Operating Activities, Total	47	103
Cash Flows from Investing Activities:
Capital expenditures	(314)	(286)
Decrease (increase) in notes receivable–affiliated companies	(665)	481
Other, net	(3)	(3)
Net Cash Provided by (Used in) Investing Activities, Total	(982)	192
Cash Flows from Financing Activities:
Proceeds from long-term debt	1,096	0
Payments of long-term debt	(138)	(63)
Increase (decrease) in notes payable–affiliated companies	(8)	133
Dividend to parent	0	(385)
Payment of debt issuance costs	(10)	0
Net cash provided by (used in) financing activities from continuing operations	940	(315)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	5	(20)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	154	235
Cash, Cash Equivalents and Restricted Cash at End of Period	159	215
CERC Corp [Member]
Cash Flows from Operating Activities:
Net income (loss)	151	67
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	80	74
Amortization of deferred financing costs	1	3
Deferred income taxes	41	23
Goodwill impairment and loss from reclassification to held for sale	0	132
Write-down of natural gas inventory	0	3
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	(41)	169
Accounts receivable/payable–affiliated companies	(5)	0
Inventory	64	114
Accounts payable	(10)	(159)
Non-trading derivatives, net	0	(54)
Margin deposits, net	0	21
Interest and taxes accrued	18	(11)
Net regulatory assets and liabilities	(2,065)	10
Other current assets	2	(1)
Other current liabilities	(13)	(13)
Other non-current assets	(2)	18
Other non-current liabilities	(8)	(15)
Net Cash Provided by (Used in) Operating Activities, Total	(1,787)	381
Cash Flows from Investing Activities:
Capital expenditures	(133)	(176)
Other, net	2	(1)
Net Cash Provided by (Used in) Investing Activities, Total	(131)	(177)
Cash Flows from Financing Activities:
Proceeds from (payments of) commercial paper, net	226	(172)
Proceeds from long-term debt	1,699	0
Dividend to parent	0	(32)
Payment of debt issuance costs	(6)	0
Other, net	(1)	(1)
Net cash provided by (used in) financing activities from continuing operations	1,918	(205)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	0	(1)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	1	2
Cash, Cash Equivalents and Restricted Cash at End of Period	$ 1	$ 1