Related-Party Transactions - Summary of (Income) Expenses Incurred With Affiliated Entities (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Related Party Transaction [Line Items]
Coal sales		$ (267,337)	$ (238,387)
Type of revenue		felp:CoalMember	felp:CoalMember
Purchased coal		$ 2,375	$ 1,751
Goods and services provided		(67)	(648)
Murray Energy and Affiliated Entities (Including Javelin)
Related Party Transaction [Line Items]
Coal sales	[1]	$ (141,512)	$ (85,082)
Type of revenue		felp:CoalMember	felp:CoalMember
Purchased coal	[2]	$ 2,375	$ 1,751
Transportation services on certain export sales	[3]	2,311	978
Sales and marketing expenses	[4]	2,068	1,266
Goods and services purchased	[5]	1,772	4,118
Goods and services provided	[6]	(25)	(100)
Management services	[4]	4,285	3,983
Murray Energy and Affiliated Entities (Including Javelin) | Transport Lease Revenues
Related Party Transaction [Line Items]
Other income	[7]	(1,215)	(1,594)
Murray Energy and Affiliated Entities (Including Javelin) | ORRA
Related Party Transaction [Line Items]
Other income	[7]	(520)	(701)
Murray Energy and Affiliated Entities (Including Javelin) | Terminal Revenues
Related Party Transaction [Line Items]
Other income	[7]		(44)
Foresight Reserves and Affiliated Entities
Related Party Transaction [Line Items]
Royalty expense	[8]	6,507	5,387
Land leases	[3],[8]	$ 82	$ 60

[1] Coal sales

[2] Cost of coal purchased

[3] Transportation

[4] Selling, general and administrative

[5] Cost of coal produced (excluding depreciation, depletion and amortization) and property, plant and equipment, net, as applicable

[6] Other operating (income) expense, net

[7] Other revenues

[8] Cost of coal produced (excluding depreciation, depletion and amortization)