Regulatory Matters Regulatory Assets and Liabilities (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets, Noncurrent		$ 2,211	$ 2,629
Regulatory liabilities		542	537
Unrecognized Equity Return	[1]	(393)	(442)
Total regulatory assets and liabilities, net		1,669	2,092
Amount of allowed equity return on the true-up balance that was recognized in the period		49	68	$ 45
Other Regulatory Assets (Liabilities) [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets, Noncurrent	[2]	88	122
Pension And Postretirement Related Regulatory Asset [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets, Noncurrent		50	107
Loss on Reacquired Debt [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets, Noncurrent		93	104
Securitized Regulatory Asset Member
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory Assets, Noncurrent		2,373	2,738
Removal Costs [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities		350	353
Other Regulatory Assets (Liabilities) [Member]
Schedule Of Regulatory Assets And Liabilities [Line Items]
Regulatory liabilities		$ 192	$ 184

[1] As of December 31, 2015, CenterPoint Houston has not recognized an allowed equity return of $393 million because such return will be recognized as it is recovered in rates through 2024. During the years ended December 31, 2015, 2014 and 2013, CenterPoint Houston recognized approximately $49 million, $68 million and $45 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, 2015 and 2014.