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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

This represents a distribution to ZENS holders during the period in accordance with the terms of the ZENS.

No definition available.

Name:	cnp_DistributionToZENSHolders
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Represents the fractional shares exchanged for each TW Common share held.

No definition available.

Name:	cnp_FractionalsharesexchangedforeachTWCommonshareheld
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Data Type:	xbrli:sharesItemType
Balance Type:	na
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
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Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

Represents the amount of realized loss on indexed debt securities recognized in the period.

No definition available.

Name:	cnp_RealizedLossOnIndexedDebtSecurities
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the amount that indexed debt was reduced as a result of remittance to ZENS note holders in accordance with the terms of the ZENS.

No definition available.

Name:	cnp_ReductionInIndexedDebt
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the amount of reduction in ZENS derivative obligation due to the partial settlement

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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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
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents the total AT&T shares received in exchange for the TW Common held.

No definition available.

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Data Type:	xbrli:sharesItemType
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Period Type:	instant

Early exchange ratio on ZENS subordinated debt.

No definition available.

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

Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination.

No definition available.

Name:	us-gaap_BusinessAcquisitionSharePrice
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Data Type:	num:perShareItemType
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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Balance held at close of period in number of shares.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Name:	us-gaap_InvestmentOwnedBalanceShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

The cash inflow associated with the sale, maturities, repayments and calls of securities classified as trading securities and held for investment purposes. Excludes proceeds from trading securities purchased and held principally for the purpose of selling them in the near term (thus held for only a short period of time).

No definition available.

Name:	us-gaap_ProceedsFromSaleAndMaturityOfTradingSecuritiesHeldforinvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Name:	us-gaap_LongtermDebtTypeAxis=cnp_SubordinatedDebtZENSMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	us-gaap_BusinessAcquisitionAxis=cnp_ATTToAcquireTimeWarnerMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	us-gaap_BusinessAcquisitionAxis=cnp_MeredithtoacquiretimeMember
Namespace Prefix:
Data Type:	na
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Name:	us-gaap_FinancialInstrumentAxis=cnp_ATTCommonMember
Namespace Prefix:
Data Type:	na
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Name:	us-gaap_FinancialInstrumentAxis=cnp_CharterCommonMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	us-gaap_FinancialInstrumentAxis=cnp_TimeCommonMember
Namespace Prefix:
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