Business Combinations and Divestitures (Details) $ in Millions					9 Months Ended	11 Months Ended		12 Months Ended
	Feb. 25, 2019 USD ($)	Feb. 16, 2018	Feb. 17, 2017 USD ($) well	Oct. 01, 2015 USD ($) MMcf	Sep. 30, 2018	Jan. 31, 2019 USD ($)	Jan. 31, 2018 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2018
Business Acquisition [Line Items]
Subsidiary ownership percentage										100.00%
EnLink
Business Acquisition [Line Items]
Natural gas capacity, MMcf per day | MMcf				35
Proceeds from sale of oil and gas property and equipment				$ 143.4
Proceeds from sale of oil and gas property and equipment net of purchase price adjustments				139.8
Purchase price adjustments for production, revenues and operating and capital expenditures				$ 3.6
Gas gathering and processing agreement, term				15 years
Carrying value of net assets sold									$ 31.0
Sale leaseback transaction, deferred gain									108.4
Sale leaseback transaction, transaction costs									$ 0.4
Sale leaseback transaction, current period gain recognized								$ 107.3
Corporate Joint Venture | San Mateo Midstream
Business Acquisition [Line Items]
Subsidiary ownership percentage			51.00%
Deferred performance incentives			$ 44.1				$ 14.7
Deferred performance incentives, term		3 years			5 years
Contributions to joint venture, operating capital			$ 5.1
Corporate Joint Venture | San Mateo Midstream | Subsequent Event
Business Acquisition [Line Items]
Deferred performance incentives	$ 150.0					$ 14.7
Five Point | Corporate Joint Venture | San Mateo Midstream
Business Acquisition [Line Items]
Subsidiary ownership percentage			49.00%
Payments to acquire interest in joint venture			$ 176.4
Proceeds from divestiture of interest in joint venture			$ 171.5
Rustler Breaks and Wolf Asset Area | Corporate Joint Venture | San Mateo Midstream
Business Acquisition [Line Items]
Contractual obligation, term			15 years
Rustler Breaks Asset Area | Corporate Joint Venture | San Mateo Midstream
Business Acquisition [Line Items]
Number of wells contributed to joint venture | well			1
Contractual obligation, term			15 years
Wolf Asset Area | Corporate Joint Venture | San Mateo Midstream
Business Acquisition [Line Items]
Number of wells contributed to joint venture | well			3