For an unclassified balance sheet, amounts due from related parties including affiliates, employees, joint ventures, officers and stockholders, immediate families thereof, and pension funds.

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Name:	us-gaap_DueFromRelatedParties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Related Party Transactions (Details) - Flatonia Energy, LLC - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Related Party Transaction [Line Items]
Payments made to related party	$ 4.0	$ 6.1	$ 8.3	$ 12.4
Payments received from related party	1.6	$ 2.0	2.9	$ 4.1
Amounts receivable from related party	1.0		1.0		$ 0.8
Amounts payable to related party	$ 1.3		$ 1.3		$ 1.6
Class A Common Stock
Related Party Transaction [Line Items]
Percentage of common stock acquired			10.20%
Common Class A and Common Class B
Related Party Transaction [Line Items]
Percentage of common stock acquired			4.60%