Name:	cnp_DebtInstrumentContingentPrincipalAmountOutstanding
Namespace Prefix:	cnp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Number of shares attributable to each note and referenced in determining the fair value of the cash to be exchange at behest of note holder.

No definition available.

Name:	cnp_NumberOfSharesReferencedInExchangeableSubordinatedNote
Namespace Prefix:	cnp_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

The percentage of the fair value of the referenced TW Common shares attributable to each note and the percentage of composite fair value each note can be exchanged for cash.

No definition available.

Name:	cnp_SubordinatedNoteCashExchangeablePercentageOfFairValue
Namespace Prefix:	cnp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

The target annual yield from interest and cash dividends on reference shares, before any adjustment to increase or decrease principal amount of subordinated note is made.

No definition available.

Name:	cnp_TargetAnnualYieldOnReferenceShares
Namespace Prefix:	cnp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Face (par) amount of debt instrument at time of issuance.

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Name:	us-gaap_DebtInstrumentFaceAmount
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Contractual interest rate for funds borrowed, under the debt agreement.

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Balance held at close of period in number of shares.

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