Background (Details) - state	Dec. 31, 2017	Dec. 31, 2016	[1]	Dec. 31, 2015
Enable Midstream Partners [Member]
Equity method investment ownership percentage	54.10%	54.10%		55.40%
Natural Gas Distribution [Member]
Number of states in which entity operates	6
Energy Services [Member]
Number of states in which entity operates	33

[1] In November 2016, Enable completed a public offering of 11,500,000 common units of which 1,424,281 were sold by ArcLight Capital Partners, LLC. The common units issued and sold by Enable resulted in dilution of both CERC Corp.’s and OGE’s limited partner interest in Enable.