CONDENSED CONSOLIDATED BALANCE SHEETS (Parentheticals) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Cash and cash equivalents	$ 328	$ 260
Accounts receivable, less bad debt reserve	958	1,000
Bad debt reserve	21	19
Prepaid expenses and other current assets	167	241
Regulatory assets	$ 2,067	$ 2,347
Cumulative preferred stock par value (in dollars per share)	$ 0.01	$ 0.01
Cumulative preferred stock authorized (in shares)	20,000,000	20,000,000
Cumulative preferred stock outstanding (in shares)	0	0
Common stock par value (in dollars per share)	$ 0.01	$ 0.01
Common stock authorized (in shares)	1,000,000,000	1,000,000,000
Common stock outstanding (in shares)	431,547,782	431,044,845
Variable Interest Entity, Primary Beneficiary [Member]
Cash and cash equivalents	$ 253	$ 230
Accounts receivable, less bad debt reserve	112	73
Prepaid expenses and other current assets	37	35
Regulatory assets	1,293	1,590
Houston Electric [Member]
Cash and cash equivalents	253	238
Bad debt reserve	1	1
Prepaid expenses and other current assets	59	62
Regulatory assets	1,321	1,570
Houston Electric [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Cash and cash equivalents	253	230
Accounts receivable, less bad debt reserve	112	73
Prepaid expenses and other current assets	37	35
Regulatory assets	1,293	1,590
CERC Corp [Member]
Cash and cash equivalents	1	12
Accounts receivable, less bad debt reserve	566	713
Bad debt reserve	20	18
Prepaid expenses and other current assets	80	166
Regulatory assets	$ 173	$ 181