Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2021

Fair Value Disclosures [Abstract]

Fair value, assets and liabilities measured on a recurring basis [Table Text Block]

The following tables present information about the Registrants’ assets and liabilities measured at fair value on a recurring basis as of March 31, 2021 and December 31, 2020 and indicate the fair value hierarchy of the valuation techniques utilized by the Registrants to determine such fair value.

CenterPoint Energy

	March 31, 2021								December 31, 2020
	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Assets	(in millions)
Corporate equities	$	850	$	—	$	—	$	850	$	873	$	—	$	—	$	873
Investments, including money market funds (1)	43		—		—		43		43		—		—		43
Total assets	$	893	$	—	$	—	$	893	$	916	$	—	$	—	$	916
Liabilities
Indexed debt securities derivative	$	—	$	927	$	—	$	927	$	—	$	953	$	—	$	953
Interest rate derivatives	—		9		—		9		—		20		—		20
Natural gas derivatives	—		7		—		7		—		10		—		10
Total liabilities	$	—	$	943	$	—	$	943	$	—	$	983	$	—	$	983

Houston Electric

	March 31, 2021								December 31, 2020
	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Assets	(in millions)
Investments, including money market funds (1)	$	27	$	—	$	—	$	27	$	26	$	—	$	—	$	26
Total assets	$	27	$	—	$	—	$	27	$	26	$	—	$	—	$	26

CERC

	March 31, 2021								December 31, 2020
	Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3		Total
Assets	(in millions)
Corporate equities	$	2	$	—	$	—	$	2	$	2	$	—	$	—	$	2
Investments, including money market funds (1)	11		—		—		11		11		—		—		11
Total assets	$	13	$	—	$	—	$	13	$	13	$	—	$	—	$	13

(1)Amounts are included in Prepaid expenses and other current assets in the Condensed Consolidated Balance Sheets.

Estimated fair value of financial instruments, debt instruments [Table Text Block]

The fair values of cash and cash equivalents, investments in debt and equity securities measured at fair value and short-term borrowings are estimated to be approximately equivalent to carrying amounts and have been excluded from the table below. The carrying amounts of non-trading derivative assets and liabilities and CenterPoint Energy’s ZENS indexed debt securities derivative are stated at fair value and are excluded from the table below. The fair value of each debt instrument is determined by multiplying the principal amount of each debt instrument by a combination of historical trading prices and comparable issue data. These liabilities, which are not measured at fair value in the Registrants’ Condensed Consolidated Balance Sheets, but for which the fair value is disclosed, would be classified as Level 2 in the fair value hierarchy.

	March 31, 2021						December 31, 2020
	CenterPoint Energy (1)		Houston Electric (1)		CERC		CenterPoint Energy (1)		Houston Electric (1)		CERC
Long-term debt, including current maturities	(in millions)
Carrying amount	$	15,823	$	5,968	$	4,349	$	13,401	$	5,019	$	2,428
Fair value	16,848		6,485		4,580		15,226		5,957		2,855

(1)Includes Securitization Bonds debt.