Investment in Unconsolidated Affiliates (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020		Mar. 31, 2019	Dec. 31, 2019
Expected Settlement Charge	$ 17.0
Limited Partner Units Owned	111.0
Distribution Made to Limited Partner, Distributions Declared, Per Unit	$ 0.16525		$ 0.33050
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest	25.50%		25.50%
Equity in earnings (losses) of unconsolidated affiliates	$ (746.5)	[1]	$ 30.7
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	1,424.3			$ 652.5
Enable Midstream Partners [Member]
Distributions from unconsolidated affiliates	$ 36.7		$ 35.3
OGE Holdings [Member]
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest	25.50%
Enable Midstream Partners [Member]
Share Price	$ 2.57

[1] At March 31, 2020, the Company recorded a $780.0 million impairment on its investment in Enable, as further discussed in Notes 4 and 5.