Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands, shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Related Party Transaction [Line Items]
Non-cash contributions			$ 200
Amount payable to related parties	$ 829		829		$ 801
Operating and maintenance expenses—affiliates, net	4,062	$ 1,744	9,948	$ 8,090
Revenues and other income	91,448	112,199	284,667	326,874
Deferred revenue—affiliates	74,663		74,663		82,853
Contracts receivable—affiliate, current and long-term	47,542		47,542		49,948
Accounts receivable	7,057		7,057		6,345
General Partner
Related Party Transaction [Line Items]
Non-cash contributions			200
Quintana Minerals
Related Party Transaction [Line Items]
Amount payable to related parties	500		500		1,100
Operating and maintenance expenses—affiliates, net	400	1,200	200	600
Western Pocahontas Properties
Related Party Transaction [Line Items]
Amount payable to related parties	500		500		300
Cline Affiliates
Related Party Transaction [Line Items]
Operating and maintenance expenses—affiliates, net	400	300	$ 1,000	1,000
Rate of interest in the partnerships general partner (percent)			31.00%
Related party transaction number of units hold by the related party in partnerships' general partner (in shares)			0.5
Accounts receivable	6,900		$ 6,900		6,400
Net amount receivable					4,900
Accounts receivable					1,500
Cline Affiliates
Related Party Transaction [Line Items]
Deferred revenue—affiliates	74,700		74,700		82,600
Net amount receivable	2,700		2,700
Accounts receivable	1,400		1,400
Foresight Energy Lp | Coal Sales
Related Party Transaction [Line Items]
Revenues and other income	20,600	18,700	47,600	68,600
Sugar Camp
Related Party Transaction [Line Items]
Contracts receivable—affiliate, current and long-term	77,700		77,700		81,200
Unearned income	32,700		32,700		35,300
Net amount receivable	45,000		45,000		45,900
Accounts receivable	2,100		2,100		2,000
Corsa
Related Party Transaction [Line Items]
Deferred revenue—affiliates	300		300		300
Accounts receivable	200		200		200
Royalty Revenue from Coal	800	900	1,900	2,400
Western Pocahontas Properties Limited Partnership | Affiliated Entity
Related Party Transaction [Line Items]
Operating and maintenance expenses—affiliates, net	0	(100)	700	0
Other assets—affiliate	$ 1,000		$ 1,000		1,100
Senior Notes Due 2018 | Cline Trust Company
Related Party Transaction [Line Items]
Partnership common units owned (in shares)	0.5		0.5
Principal amount of partnership purchased			$ 20,000
Rate of senior notes (percent)	9.125%		9.125%
Senior notes due	$ 19,900		$ 19,900
Discontinued Operations, Held-for-sale [Member] | Quintana Minerals
Related Party Transaction [Line Items]
Amount payable to related parties	100		100		$ 700
Foresight Energy Lp
Related Party Transaction [Line Items]
Revenues	$ 20,635	$ 18,677	$ 47,648	$ 68,556