Commitments and Contingencies (Details) (USD $)	3 Months Ended
	Mar. 31, 2014
Recorded Unconditional Purchase Obligation Payment Schedule [Abstract]
2014	$ 206,000,000
2015	363,000,000
2016	311,000,000
2017	247,000,000
2018	240,000,000
After 2018	120,000,000
LegalEnvironmentalAndOtherRegulatoryMattersLegalMattersGasMarketManipulationCasesAbstract
Recovery of compensatory damages sought by plaintiffs	in excess of $1 billion
Approximate number of gas market manipulatioin lawsuits naming CenterPoint Energy and/or Reliant Energy (in number of lawsuits)	30
Number of gas market manipulation lawsuits pending for CenterPoint and its affiliates (in number of lawsuits)	1
Site Contingency Completed Remediation	2
Number of remaining sites in the Minnesota service territory (in number of sites)	5
Number of remaining sites in the Minnesota service territory where the company believes it has no liability (in number of sites)	2
Accrual for Environmental Loss Contingencies	14,000,000
Annual amount included in rates to fund normal on-going remediation costs	285,000
Amount collected from insurance companies to be used for future environmental remediation	6,400,000
Approximate amount of undiscounted maximum potential guarantee obligation	55,000,000
Midstream Partnership [Member]
LegalEnvironmentalAndOtherRegulatoryMattersLegalMattersGasMarketManipulationCasesAbstract
Guarantor Obligations, Current Amount	1,050,000,000
Maximum [Member]
LegalEnvironmentalAndOtherRegulatoryMattersLegalMattersGasMarketManipulationCasesAbstract
Maximum estimated remediation costs for the Minnesota sites	41,000,000
Minimum years of remediation for the Minnesota sites (in years)	50
Minimum [Member]
LegalEnvironmentalAndOtherRegulatoryMattersLegalMattersGasMarketManipulationCasesAbstract
Maximum estimated remediation costs for the Minnesota sites	$ 6,000,000
Minimum years of remediation for the Minnesota sites (in years)	30