Reportable Business Segments Revenue by Products and Services (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended									12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013		Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue from External Customers	$ 1,689	$ 964	$ 1,183	$ 2,531	$ 1,543	$ 891	$ 1,235	[1]	$ 1,853	$ 6,367	$ 5,522	$ 4,901
Retail Gas Sales [Member]
Revenue from External Customers										5,049	4,150	3,328
Wholesale Gas Sales [Member]
Revenue from External Customers										1,159	913	613
Gas Transportation and Processing [Member]
Revenue from External Customers										38	345	847
Energy Products Or Services [Member]
Revenue from External Customers										$ 121	$ 114	$ 113

[1] Effective May 1, 2013, CERC Corp. contributed CenterPoint Midstream to Enable. See Note 2(b) and Note 10 for further discussion on the formation of Enable and CERC’s investment in Enable, respectively.