STATEMENTS OF CONSOLIDATED COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net Income (Loss)	$ (773)	$ 791	$ 368
Other comprehensive income (loss):
Adjustment to pension and other postretirement plans	(5)	12	(10)
Net deferred gain (loss) from cash flow hedges	0	(2)	(15)
Reclassification of net deferred losses from cash flow hedges	15	0	0
Other comprehensive loss from unconsolidated affiliates, net of tax	(2)	(1)	0
Total	8	10	(25)
Comprehensive income (loss)	(765)	801	343
Income allocated to preferred shareholders	176	117	35
Comprehensive income (loss) available to common shareholders	(941)	684	308
Supplemental Income Statement Elements [Abstract]
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax, Attributable to Parent	0	4	(2)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax	0	(1)	(4)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	0	0	0
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax	4	0	0
Other comprehensive loss from unconsolidated affiliates, tax	0	0	0
Houston Electric [Member]
Net Income (Loss)	334	356	336
Other comprehensive income (loss):
Net deferred gain (loss) from cash flow hedges	0	(1)	(14)
Reclassification of net deferred losses from cash flow hedges	15	0	0
Total	15	(1)	(14)
Comprehensive income (loss) available to common shareholders	349	355	322
Supplemental Income Statement Elements [Abstract]
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax	0	0	(4)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax	4	0	0
CERC Corp [Member]
Net Income (Loss)	81	212	208
Other comprehensive income (loss):
Adjustment to pension and other postretirement plans	0	5	1
Net deferred gain (loss) from cash flow hedges	0	0	(1)
Total	0	5	0
Comprehensive income (loss) available to common shareholders	81	217	208
Supplemental Income Statement Elements [Abstract]
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax, Attributable to Parent	1	2	1
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax	$ 0	$ 0	$ 0