Derivatives - Components of Gain (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivatives
Realized gain (loss) on derivatives	$ 7.0	$ 11.2	$ (10.5)
Gain (loss) on derivative activity	5.2	(4.2)	(11.1)
EnLink Midstream Partners, LP | Commodity Swaps
Derivatives
Change in fair value of derivatives	10.1	4.7	(20.1)
Realized gain (loss) on derivatives	(4.9)	(8.9)	9.0
Gain (loss) on derivative activity	$ 5.2	$ (4.2)	$ (11.1)