STATEMENTS OF CONSOLIDATED CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flows from Operating Activities:
Net income	$ 791	$ 368	$ 1,792
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,287	1,243	1,036
Amortization of deferred financing costs	29	48	24
Deferred income taxes	69	48	(770)
Goodwill impairment charge recorded from annual impairment test	48	0	0
Amortization expense of intangible assets recorded in Depreciation and amortization (1) (2)	24	0	0
Unrealized loss (gain) on marketable securities	(282)	22	(7)
Loss (gain) on indexed debt securities	292	232	(49)
Write-down of natural gas inventory	4	2	0
Income (Loss) from Equity Method Investments	(230)	(307)	(265)
Proceeds from Equity Method Investment, Distribution	261	267	0
Pension contributions	(109)	(69)	(48)
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	226	(154)	(216)
Inventory	(52)	1	(7)
Taxes receivable	(106)	0	30
Accounts payable	(455)	220	136
Fuel cost recovery	92	33	(85)
Non-trading derivatives, net	(64)	103	(84)
Margin deposits, net	(56)	5	(55)
Interest and taxes accrued	54	40	5
Net regulatory assets and liabilities	(114)	28	(107)
Other current assets	(22)	0	(3)
Other current liabilities	(107)	(24)	34
Other assets	103	6	(4)
Other liabilities	(54)	12	36
Other, net	9	12	24
Net cash provided by operating activities	1,638	2,136	1,417
Cash Flows from Investing Activities:
Capital expenditures	(2,506)	(1,651)	(1,426)
Acquisitions, net of cash acquired	(5,991)	0	(132)
Distributions from unconsolidated affiliates in excess of cumulative earnings	42	30	297
Proceeds from sale of marketable securities	0	398	0
Proceeds from sale of assets	5	0	0
Purchase of investments	(6)	0	0
Other, net	35	16	4
Net cash provided by (used in) investing activities	(8,421)	(1,207)	(1,257)
Cash Flows from Financing Activities:
Increase (decrease) in short-term borrowings, net	0	(39)	4
Proceeds from (payments of) commercial paper, net	1,891	(1,543)	349
Proceeds from long-term debt, net	2,916	2,495	1,096
Payments of long-term debt	(1,302)	(484)	(1,211)
Loss on reacquired debt	0	0	(5)
Debt and equity issuance costs	(20)	(47)	(13)
Payment of dividends on Common Stock	(577)	(499)	(461)
Payment of dividends on preferred stock	(118)	(11)	0
Proceeds from issuance of Common Stock, net	0	1,844	0
Proceeds from issuance of preferred stock, net	0	1,740	0
Distribution to ZENS holders	0	(398)	0
Other, net	(14)	(5)	(4)
Net cash provided by (used in) financing activities	2,776	3,053	(245)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(4,007)	3,982	(85)
Cash, Cash Equivalents and Restricted Cash at Beginning of Year	4,278	296	381
Cash, Cash Equivalents and Restricted Cash at End of Year	271	4,278	296
Houston Electric [Member]
Cash Flows from Operating Activities:
Net income	356	336	433
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	648	917	724
Amortization of deferred financing costs	12	11	13
Deferred income taxes	(24)	(38)	(98)
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	38	11	(73)
Accounts receivable/payable–affiliated companies	(23)	20	(46)
Inventory	(12)	(16)	15
Taxes receivable	5	(5)	6
Accounts payable	13	(1)	59
Non-trading derivatives, net	(25)	5	0
Interest and taxes accrued	13	(2)	7
Net regulatory assets and liabilities	(48)	(97)	(148)
Other current assets	(5)	(2)	(6)
Other current liabilities	(9)	(26)	16
Other assets	5	(3)	13
Other liabilities	(12)	17	(4)
Other, net	(14)	(12)	(6)
Net cash provided by operating activities	918	1,115	905
Cash Flows from Investing Activities:
Capital expenditures	(1,025)	(922)	(875)
(Increase) decrease in notes receivable–affiliated companies	(481)	0	96
Other, net	11	11	3
Net cash provided by (used in) investing activities	(1,495)	(911)	(776)
Cash Flows from Financing Activities:
Proceeds from long-term debt, net	696	398	298
Payments of long-term debt	(458)	(434)	(411)
Dividend to parent	(376)	(209)	(180)
Increase (decrease) in notes payable–affiliated companies	(1)	(59)	60
Debt issuance costs	(8)	(4)	(3)
Contribution from parent	590	200	0
Other, net	(1)	0	0
Net cash provided by (used in) financing activities	442	(108)	(236)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(135)	96	(107)
Cash, Cash Equivalents and Restricted Cash at Beginning of Year	370	274	381
Cash, Cash Equivalents and Restricted Cash at End of Year	235	370	274
CERC Corp [Member]
Cash Flows from Operating Activities:
Net income	212	208	745
Income (loss) from discontinued operations, net of tax	0	138	161
Income (loss) from continuing operations	212	70	584
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	305	293	279
Amortization of deferred financing costs	9	9	9
Deferred income taxes	7	31	(224)
Goodwill impairment charge recorded from annual impairment test	48	0	0
Write-down of natural gas inventory	4	2	0
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	252	(155)	(143)
Accounts receivable/payable–affiliated companies	(6)	9	0
Inventory	(12)	17	(22)
Accounts payable	(305)	163	64
Fuel cost recovery	86	33	(85)
Non-trading derivatives, net	(60)	98	(82)
Margin deposits, net	(56)	5	(55)
Interest and taxes accrued	2	0	(41)
Net regulatory assets and liabilities	(10)	50	(27)
Other current assets	1	4	2
Other current liabilities	22	(3)	15
Other assets	5	5	(8)
Other liabilities	(38)	6	6
Other, net	0	1	6
Net cash provided by operating activities from continuing operations	466	638	278
Net cash provided by operating activities from discontinued operations	0	176	0
Net cash provided by operating activities	466	814	278
Cash Flows from Investing Activities:
Capital expenditures	(776)	(633)	(513)
Acquisitions, net of cash acquired	0	0	(132)
(Increase) decrease in notes receivable–affiliated companies	114	(114)	0
Other, net	0	3	2
Net cash used in investing activities from continuing operations	(662)	(744)	(643)
Net cash provided by investing activities from discontinued operations	0	47	297
Net cash provided by (used in) investing activities	(662)	(697)	(346)
Cash Flows from Financing Activities:
Increase (decrease) in short-term borrowings, net	0	(39)	4
Proceeds from (payments of) commercial paper, net	167	(688)	329
Proceeds from long-term debt, net	0	599	298
Payments of long-term debt	0	0	(550)
Dividend to parent	(120)	(360)	(601)
Increase (decrease) in notes payable–affiliated companies	0	(570)	570
Loss on reacquired debt	0	0	(5)
Debt issuance costs	0	(5)	(4)
Contribution from parent	129	960	38
Other, net	(3)	(1)	0
Net cash used in financing activities from continuing operations	173	(104)	79
Net cash provided by financing activities from discontinued operations	0	0	0
Net cash provided by (used in) financing activities	173	(104)	79
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(23)	13	11
Cash, Cash Equivalents and Restricted Cash at Beginning of Year	25	12	1
Cash, Cash Equivalents and Restricted Cash at End of Year	$ 2	$ 25	$ 12