Investment in Unconsolidated Affiliates (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	May 01, 2013
Expected Settlement Charge			$ 12.0
Limited Partner Units Owned	111.0		111.0
Distribution Made to Limited Partner, Distributions Declared, Per Unit			$ 0.33050
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest	25.50%	25.60%	25.50%	25.60%
Equity in earnings of unconsolidated affiliates	$ 35.8	$ 29.3	$ 66.5	$ 63.2
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	666.8		666.8		$ 680.3
Enogex LLC [Member]
Increase in fair value of net assets						$ 2,200.0
Enable Midstream Partners [Member]
Distributions from unconsolidated affiliates	$ 35.3	$ 35.3	$ 70.6	$ 70.6
OGE Holdings [Member]
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest			25.50%
Enable Midstream Partners [Member]
Share Price	$ 13.71		$ 13.71