Related Party Transactions (Details) - Flatonia Energy, LLC - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Related Party Transaction [Line Items]
Payments made to related party	$ 0	$ 6,400,000	$ 12,400,000	$ 20,800,000
Payments received from related party	700,000	$ 800,000	4,800,000	$ 3,200,000
Amounts receivable from related party	800,000		800,000		$ 1,300,000
Amounts payable to related party	$ 0		$ 0		$ 0
Class A Common Stock
Related Party Transaction [Line Items]
Percentage of common stock acquired			10.30%
Common Stock
Related Party Transaction [Line Items]
Percentage of common stock acquired			4.60%