Intangible Assets (Details) (USD $)	12 Months Ended			0 Months Ended	3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 16, 2014	Dec. 31, 2014
Finite-Lived Intangible Assets, Net [Abstract]
Net Balance	$ 60,821,000	$ 59,685,000			$ 60,821,000
Goodwill	6,253,000	0			6,253,000
Amortization of intangible assets	3,300,000	3,668,000	2,802,000
Weston Products, LLC
Finite-Lived Intangible Assets, Net [Abstract]
Preliminary purchase price				25,400,000
Intangible assets	10,100,000				10,100,000
Goodwill	6,253,000				6,253,000
HBB
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	10,100,000				10,100,000
Accumulated Amortization	(58,000)				(58,000)
Net Balance	10,042,000				10,042,000
Expected annual amortization expense, 2015	1,400,000				1,400,000
Expected annual amortization expense, 2016	1,400,000				1,400,000
Expected annual amortization expense, 2017	1,400,000				1,400,000
Expected annual amortization expense, 2018	1,400,000				1,400,000
Expected annual amortization expense, 2019	1,400,000				1,400,000
Coal supply agreement amortization period	9 years
HBB | Customer Relationships
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	5,760,000				5,760,000
Accumulated Amortization	(40,000)				(40,000)
Net Balance	5,720,000				5,720,000
HBB | Trademarks
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	3,100,000				3,100,000
Accumulated Amortization	(8,000)				(8,000)
Net Balance	3,092,000				3,092,000
HBB | Other Intangible Assets
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	1,240,000				1,240,000
Accumulated Amortization	(10,000)				(10,000)
Net Balance	1,230,000				1,230,000
NACoal
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	84,200,000	92,430,000			84,200,000
Accumulated Amortization	(33,421,000)	(32,745,000)			(33,421,000)
Net Balance	50,779,000	59,685,000			50,779,000
Expected annual amortization expense, 2015	2,700,000				2,700,000
Expected annual amortization expense, 2016	2,700,000				2,700,000
Expected annual amortization expense, 2017	2,800,000				2,800,000
Expected annual amortization expense, 2018	2,800,000				2,800,000
Expected annual amortization expense, 2019	2,800,000				2,800,000
Coal supply agreement amortization period	30 years
NACoal | Other Intangible Assets
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	0	950,000			0
Accumulated Amortization	0	(253,000)			0
Net Balance	0	697,000			0
NACoal | Coal Supply Agreement
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	84,200,000	91,480,000			84,200,000
Accumulated Amortization	(33,421,000)	(32,492,000)			(33,421,000)
Net Balance	50,779,000	58,988,000			50,779,000
Reed Minerals | NACoal
Finite-Lived Intangible Assets, Net [Abstract]
Reed Minerals long-lived asset impairment charge					105,100,000
Reed Minerals | NACoal | Coal Supply Agreement
Finite-Lived Intangible Assets, Net [Abstract]
Amount allocated to identifiable intangible assets	0				0
Reed Minerals | Finite-Lived Intangible Assets | NACoal
Finite-Lived Intangible Assets, Net [Abstract]
Reed Minerals long-lived asset impairment charge					$ 5,700,000