Regulatory Matters Regulatory Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets, Noncurrent	$ 2,629		$ 3,001
Regulatory liabilities	537		509
Unrecognized Equity Return	(442)	[1]	(508)	[1]
Total regulatory assets and liabilities, net	2,092		2,492
Amount of allowed equity return on the true-up balance that was recognized in the period	68		45		47
Remaining amounts of regulatory assets for which no return on investment during recovery period is provided	0		5
Other Regulatory Assets (Liabilities) [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets, Noncurrent	122	[2]	129	[2]
Pension And Postretirement Related Regulatory Asset [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets, Noncurrent	107	[3]	90	[3]
Loss on Reacquired Debt [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets, Noncurrent	104		111
Securitized Regulatory Asset Member
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets, Noncurrent	2,738		3,179
Removal Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities	353		349
Other Regulatory Assets (Liabilities) [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities	$ 184		$ 160

[1] As of December 31, 2014, CenterPoint Houston has not recognized an allowed equity return of $442 million because such return will be recognized as it is recovered in rates through 2024. During the years ended December 31, 2014, 2013 and 2012, CenterPoint Houston recognized approximately $68 million, $45 million and $47 million, respectively, of the allowed equity return. The timing of CenterPoint Houston’s recognition of the allowed equity return will vary each period based on amounts actually collected during the period. The actual amounts recovered for the allowed equity return are reviewed and adjusted at least annually by the Texas Utility Commission to correct any over-collections or under-collections during the preceding 12 months and to provide for the full and timely recovery of the allowed equity return.

[2] Other regulatory assets that are not earning a return were not material as of December 31, 2014 and 2013. As of December 31, 2013, the amount is presented after the effect of the revisions to the prior period financial statement discussed in Note 2(n).

[3] CenterPoint Houston’s actuarially determined pension and other postemployment expense in excess of the amount being recovered through rates is being deferred for rate making purposes. Deferred pension and other postemployment expenses of $-0- and $5 million as of December 31, 2014 and 2013, respectively, were not earning a return.