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Related Party Transactions - Narrative (Details) - Affiliated Entity - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Quintana Minerals
Related Party Transaction [Line Items]
Accounts payable to related parties	$ 0.4		$ 0.4		$ 0.4
Western Pocahontas Properties Limited Partnership
Related Party Transaction [Line Items]
Accounts payable to related parties	0.3		0.3		0.3
Operating and maintenance expenses	$ 0.9	$ 0.2	$ 2.1	$ 0.3
Accounts Receivable, Related Parties, Noncurrent					$ 0.3