CONDENSED STATEMENTS OF CONSOLIDATED CASH FLOWS (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash Flows from Operating Activities:
Net income	$ 169	$ 165
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	313	314
Amortization of deferred financing costs	7	6
Amortization of intangible assets in non-utility cost of revenues	9	0
Deferred income taxes	(14)	(17)
Unrealized gain on marketable securities	(83)	(1)
Loss on indexed debt securities	86	18
Write-down of natural gas inventory	1	1
Equity in earnings of unconsolidated affiliate, net of distributions	12	(9)
Pension contributions	(2)	(62)
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	138	39
Inventory	120	139
Accounts payable	(332)	(209)
Fuel cost recovery	58	64
Non-trading derivatives, net	(40)	64
Margin deposits, net	19	(28)
Interest and taxes accrued	(116)	(32)
Net regulatory assets and liabilities	(3)	42
Other current assets	16	(15)
Other current liabilities	(101)	1
Other assets	58	(3)
Other liabilities	(39)	5
Other operating activities, net	(5)	2
Net cash provided by operating activities	271	484
Cash Flows from Investing Activities:
Capital expenditures	(537)	(362)
Acquisitions, net of cash acquired	(5,987)	0
Distributions from unconsolidated affiliate in excess of cumulative earnings	0	14
Proceeds from sale of marketable securities	0	16
Other investing activities, net	(15)	1
Net cash used in investing activities	(6,539)	(331)
Cash Flows from Financing Activities:
Increase (decrease) in short-term borrowings, net	0	(39)
Proceeds from (payments of) commercial paper, net	2,692	(837)
Proceeds from long-term debt, net	721	997
Payments of long-term debt	(994)	(165)
Long-term revolving credit facility	135	0
Debt issuance costs	(8)	(7)
Payment of dividends on Common Stock	(144)	(120)
Payment of dividends on Preferred Stock	(43)	0
Distribution to ZENS note holders	0	(16)
Other financing activities, net	(14)	(5)
Net cash provided by (used in) financing activities	2,345	(192)
Net Decrease in Cash, Cash Equivalents and Restricted Cash	(3,923)	(39)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	4,278	296
Cash, Cash Equivalents and Restricted Cash at End of Period	355	257
Houston Electric [Member]
Cash Flows from Operating Activities:
Net income	27	52
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	175	233
Amortization of deferred financing costs	3	3
Deferred income taxes	(15)	(20)
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	21	9
Accounts receivable/payable–affiliated companies	(32)	(5)
Inventory	1	4
Accounts payable	2	(16)
Taxes receivable	5	0
Non-trading derivatives, net	25	0
Interest and taxes accrued	(58)	(54)
Net regulatory assets and liabilities	(44)	(26)
Other current assets	13	2
Other current liabilities	(7)	(2)
Other assets	3	1
Other liabilities	(1)	(2)
Other operating activities, net	(2)	1
Net cash provided by operating activities	66	180
Cash Flows from Investing Activities:
Capital expenditures	(258)	(230)
Increase in notes receivable–affiliated companies	(979)	(133)
Other investing activities, net	0	(1)
Net cash used in investing activities	(1,237)	(364)
Cash Flows from Financing Activities:
Proceeds from long-term debt, net	696	398
Payments of long-term debt	(175)	(165)
Decrease in notes payable–affiliated companies	(1)	(60)
Dividend to parent	(24)	(32)
Contribution from parent	590	0
Debt issuance costs	(7)	(3)
Other financing activities, net	(1)	1
Net cash provided by (used in) financing activities	1,078	139
Net Decrease in Cash, Cash Equivalents and Restricted Cash	(93)	(45)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	370	274
Cash, Cash Equivalents and Restricted Cash at End of Period	277	229
CERC Corp [Member]
Cash Flows from Operating Activities:
Net income	138	130
Less: Income from discontinued operations, net of tax	0	52
Income from continuing operations	138	78
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	77	73
Amortization of deferred financing costs	3	2
Deferred income taxes	21	14
Write-down of natural gas inventory	1	1
Changes in other assets and liabilities, excluding acquisitions:
Accounts receivable and unbilled revenues, net	102	29
Accounts receivable/payable–affiliated companies	(18)	(4)
Inventory	119	135
Accounts payable	(255)	(173)
Fuel cost recovery	58	64
Non-trading derivatives, net	(26)	60
Margin deposits, net	19	(28)
Interest and taxes accrued	(8)	(10)
Net regulatory assets and liabilities	19	55
Other current assets	7	3
Other current liabilities	(8)	19
Other assets	(12)	3
Other liabilities	10	4
Other operating activities, net	1	1
Net cash provided by operating activities from continuing operations	248	326
Net cash provided by operating activities from discontinued operations	0	60
Net cash provided by operating activities	248	386
Cash Flows from Investing Activities:
Capital expenditures	(146)	(114)
Increase in notes receivable–affiliated companies	(106)	0
Other investing activities, net	2	3
Net cash used in investing activities from continuing operations	(250)	(111)
Net cash provided by investing activities from discontinued operations	0	14
Net cash used in investing activities	(250)	(97)
Cash Flows from Financing Activities:
Increase (decrease) in short-term borrowings, net	0	(39)
Proceeds from (payments of) commercial paper, net	11	(172)
Proceeds from long-term debt, net	0	599
Decrease in notes payable–affiliated companies	0	(570)
Dividend to parent	(20)	(86)
Contribution from parent	0	0
Debt issuance costs	0	(4)
Other financing activities, net	(2)	(2)
Net cash used in financing activities from continuing operations	(11)	(274)
Net cash provided by financing activities from discontinued operations	0	0
Net cash provided by (used in) financing activities	(11)	(274)
Net Decrease in Cash, Cash Equivalents and Restricted Cash	(13)	15
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	25	12
Cash, Cash Equivalents and Restricted Cash at End of Period	$ 12	$ 27