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Background and Basis of Presentation (Details)
Jun. 30, 2017
state
shares
Enable Midstream Partners [Member]  
Ownership percentage of equity method investment 54.10% [1]
Enable Midstream Partners [Member] | Series A Preferred Stock [Member]  
Preferred units held | shares 14,520,000
Natural Gas Distribution [Member]  
Number of states in which entity operates 6
Energy Services [Member]  
Number of states in which entity operates 33
[1] Excluding the Series A Preferred Units owned by CenterPoint Energy.