Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) Item	Sep. 30, 2016 USD ($)
Segment Reporting Information [Line Items]
Reported segment | Item			2
Revenues Abstract
Consolidated revenue	$ 248,884	$ 217,073	$ 673,813	$ 572,510
Capital Expenditures
Capital Expenditures			14,473	33,557
Net income (loss)	2,577	(1,584)	(24,478)	(2,670)
Interest Income	(147)	(46)	(304)	(116)
Interest expense, net	9,573	13,032	32,351	35,371
Other, Net	98	165	546	760
Income tax expense (benefit)	(115)	(647)	36	(3,226)
(Income) loss from unconsolidated affiliates, net of tax	(138)	(59)	(771)	1,018
Consolidated operating income (loss)	11,848	10,861	7,380	31,137
Depreciation and depletion	18,789	23,460	56,683	23,052
Accretion	1,865	1,065	5,532	5,641
Impairments	0	312	0	4,499
Derivative financial instruments
Exclusion of fair value mark-to-market gains (losses)	838	(1,068)	(3,102)	5,257
Inclusion of cash amounts (received) paid			1,968	3,195
Debt restructuring costs	0	4,499	23	4,499
Other	(98)	(165)	(546)	(760)
Operating Income (Loss)	11,848	10,861	7,380	31,137
Intersegment Elimination
Revenues Abstract
Consolidated revenue	(17,364)	(826)	(41,348)	(5,493)
Capital Expenditures
Consolidated operating income (loss)	(168)	(38)	(150)	(151)
Derivative financial instruments
Adjusted EBITDA	(168)	(38)	(150)	(151)
Operating Income (Loss)	(168)	(38)	(150)	(151)
Owned and Operated Mines
Derivative financial instruments
Adjusted EBITDA	45,597
Owned and Operated Mines | Operating Segments [Member]
Revenues Abstract
Consolidated revenue	197,974	212,010	550,228	531,278
Capital Expenditures
Capital Expenditures			13,053	31,800
Other, Net	98	164	548	761
Consolidated operating income (loss)	27,096	33,055	54,334	76,775
Depreciation and depletion	18,544	23,174	56,057	22,104
Accretion	1,714	859	5,079	5,177
Impairments		312		2,451
Derivative financial instruments
Exclusion of fair value mark-to-market gains (losses)	(838)	1,072	3,102	(5,203)
Inclusion of cash amounts (received) paid	(821)	(2,337)	(1,968)	(8,539)
Total derivative financial instruments	(1,659)	(1,265)	1,134	(13,742)
Other	(98)	(164)	(548)	(761)
Adjusted EBITDA	45,597	55,971	116,056	92,004
Operating Income (Loss)	27,096	33,055	54,334	76,775
Logistics and Related Activities | Operating Segments [Member]
Revenues Abstract
Consolidated revenue	67,679	3,375	161,905	20,594
Capital Expenditures
Other, Net		1	0	1,754
Consolidated operating income (loss)	(1,919)	(7,800)	(12,774)	(23,861)
Derivative financial instruments
Exclusion of fair value mark-to-market gains (losses)		(4)		(54)
Inclusion of cash amounts (received) paid		1,781		5,344
Total derivative financial instruments		1,777		5,290
Non-cash throughput amortization expense and contract termination payments	5,069		14,989
Other		(1)	0	(1,754)
Adjusted EBITDA	3,150	(6,024)	2,215	(20,325)
Operating Income (Loss)	(1,919)	(7,800)	(12,774)	(23,861)
Corporate and Other
Derivative financial instruments
Contract Buyout Proceeds	48	1,596	144	24,349
Corporate and Other | Operating Segments [Member]
Revenues Abstract
Consolidated revenue	595	2,514	3,028	26,131
Capital Expenditures
Capital Expenditures			1,420	1,757
Other, Net	(138)	(60)	(771)	(737)
Consolidated operating income (loss)	(13,160)	(14,355)	(34,030)	(21,626)
Depreciation and depletion	245	285	626	948
Accretion	151	206	453	464
Impairments				2,048
Derivative financial instruments
Debt restructuring costs		4,499	23	4,499
Non-cash throughput amortization expense and contract termination payments		0	0	0
Other	138	60	771	737
Adjusted EBITDA	(12,626)	(9,305)	(32,157)	(12,930)
Operating Income (Loss)	$ (13,160)	$ (14,355)	$ (34,030)	$ (21,626)