Short-term Borrowings and Long-term Debt - Schedule of Revolving Credit Facilities (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($)
Debt Instrument [Line Items]
Size of credit facility	$ 4,000
Houston Electric
Debt Instrument [Line Items]
Size of credit facility	300
Restoration costs	100
CERC Corp
Debt Instrument [Line Items]
Size of credit facility	$ 900
Line of Credit
Debt Instrument [Line Items]
Consecutive period for system restoration costs to exceed $100 million (in months)	12 months
Line of Credit | Maximum
Debt Instrument [Line Items]
Percentage on limitation of debt to total capitalization under covenant amended (in hundredths)	70.00%
Line of Credit | Houston Electric
Debt Instrument [Line Items]
Percentage on limitation of debt to total capitalization under covenant (as a percent)	67.50%
Ratio of indebtedness to net capital (as a percent)	0.537
Line of Credit | Houston Electric | Maximum
Debt Instrument [Line Items]
Percentage on limitation of debt to total capitalization under covenant amended (in hundredths)	70.00%
Line of Credit | CERC Corp
Debt Instrument [Line Items]
Percentage on limitation of debt to total capitalization under covenant (as a percent)	65.00%
Ratio of indebtedness to net capital (as a percent)	0.527
Line of Credit | London Interbank Offered Rate (LIBOR) | Houston Electric
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.375%
Line of Credit | London Interbank Offered Rate (LIBOR) | CERC Corp
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.25%
Parent Company
Debt Instrument [Line Items]
Size of credit facility	$ 2,400
Parent Company | Line of Credit
Debt Instrument [Line Items]
Percentage on limitation of debt to total capitalization under covenant (as a percent)	65.00%
Ratio of indebtedness to net capital (as a percent)	0.569
Parent Company | Line of Credit | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.625%
VUHI
Debt Instrument [Line Items]
Size of credit facility	$ 400
Letters of credit swing line sublimit	$ 20
VUHI | Line of Credit
Debt Instrument [Line Items]
Percentage on limitation of debt to total capitalization under covenant (as a percent)	65.00%
Ratio of indebtedness to net capital (as a percent)	0.470
VUHI | Line of Credit | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.25%