Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 16, 2014
Finite-Lived Intangible Assets, Net [Abstract]
Net Balance	$ 56,843	$ 60,821
Goodwill	6,253	6,253
Amortization of intangible assets	3,987	3,300	$ 3,668
Weston Products, LLC
Finite-Lived Intangible Assets, Net [Abstract]
Intangible assets				$ 10,100
Goodwill				$ 6,253
HBB
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	10,100
Accumulated Amortization	(1,437)
Net Balance	8,663
Expected annual amortization expense, 2016	1,400
Expected annual amortization expense, 2017	1,400
Expected annual amortization expense, 2018	1,400
Expected annual amortization expense, 2019	1,400
Expected annual amortization expense, 2020	$ 1,200
Coal supply agreement amortization period	9 years
HBB | Customer Relationships
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	$ 5,760	5,760
Accumulated Amortization	(1,000)	(40)
Net Balance	4,760	5,720
HBB | Trademarks
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	3,100	3,100
Accumulated Amortization	(208)	(8)
Net Balance	2,892	3,092
HBB | Other Intangible Assets
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	1,240	1,240
Accumulated Amortization	(229)	(10)
Net Balance	1,011	1,230
HBB | Coal Supply Agreement
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount		10,100
Accumulated Amortization		(58)
Net Balance		10,042
HBB | Weston Products, LLC
Finite-Lived Intangible Assets, Net [Abstract]
Preliminary purchase price		25,400
Intangible assets		10,100
Goodwill		6,300
HBB | Weston Products, LLC | Customer Relationships
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount		5,800
HBB | Weston Products, LLC | Trademarks
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount		3,100
HBB | Weston Products, LLC | Other Intangible Assets
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount		1,200
NACoal
Finite-Lived Intangible Assets, Net [Abstract]
Expected annual amortization expense, 2016	2,600
Expected annual amortization expense, 2017	2,800
Expected annual amortization expense, 2018	2,800
Expected annual amortization expense, 2019	2,800
Expected annual amortization expense, 2020	$ 2,800
Coal supply agreement amortization period	30 years
NACoal | Coal Supply Agreement
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	$ 84,200	84,200
Accumulated Amortization	(36,020)	(33,421)
Net Balance	$ 48,180	$ 50,779