Mergers and Acquisitions (Tables)

12 Months Ended

Dec. 31, 2018

Business Combinations [Abstract]

Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination [Table Text Block]

The fair value of the identifiable intangible assets and related useful lives included in the final purchase price allocation is as follows:

	Fair Value		Useful Life
	(in millions)		(in years)
Customer relationships	$	25	15

Business Acquisition, Pro Forma Information [Table Text Block]

The following unaudited pro forma financial information reflects the consolidated results of operations of CenterPoint Energy and CERC, assuming the AEM acquisition had taken place on January 1, 2016. The unaudited pro forma financial information has been presented for illustrative purposes only and is not necessarily indicative of the consolidated results of operations that would have been achieved had the acquisition taken place on the dates indicated or the future consolidated results of operations of the combined companies.

	Year Ended December 31,
	2017				2016
	CenterPoint Energy		CERC		CenterPoint Energy		CERC
	(in millions)
Revenues	$	9,614	$	6,603	$	8,541	$	5,467
Net Income (1)	1,792		745		442		255

(1) Net income for the year ended December 31, 2017 includes a reduction in income tax expense of $1,113 million and $396 million due to the TCJA for CenterPoint Energy and CERC, respectively. See Note 15 for further discussion of the impacts of tax reform implementation.