Current and Long-Term Financing (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Line of Credit Facility [Line Items]
Interest paid	$ 7,400,000	$ 5,300,000	$ 5,500,000
Interest capitalized	300,000	500,000
Line of credit facility, current borrowing capacity	358,696,000	362,520,000
Line of credit facility, amount outstanding	232,845,000	159,907,000
Line of credit facility, remaining borrowing capacity	125,851,000	202,613,000
Long-term debt	236,260,000
HBB
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	115,000,000
Assets held as collateral	269,700,000
Line of credit facility, unused capacity, commitment fee percentage	0.25%
Long-term Debt, Weighted Average Interest Rate	2.50%
Line of credit facility, current borrowing capacity	112,105,000	111,584,000
Line of credit facility, amount outstanding	52,845,000	18,447,000
Line of credit facility, remaining borrowing capacity	59,260,000	93,137,000
Weighted average interest rate	2.00%	3.20%
Interest rate at period end	2.50%	3.20%
Line of credit facility, minimum excess availability	25,000,000
Loan processing fee	200,000		1,200,000
KC
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	30,000,000
Assets held as collateral	50,400,000
Line of credit facility, unused capacity, commitment fee percentage	0.32%
Line of credit facility, current borrowing capacity	22,596,000	27,000,000
Line of credit facility, amount outstanding	0	1,460,000
Line of credit facility, remaining borrowing capacity	22,596,000	25,540,000
Weighted average interest rate		4.30%
Dividend restriction from closing date	2,000,000.0
Dividend restriction credit facility excess availability requirement	7,500,000.0
Minimum fixed charge coverage ratio	1.1
Loan processing fee	100,000		200,000
Dividend restriction from closing date including minimum fixed charge coverage ratio	6,000,000.0
Dividend restriction period following closing date of credit facility	12 months
Dividend restriction credit facility excess availability requirement as defined within the agreement	15,000,000.0
NACoal
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	225,000,000
Line of credit facility, unused capacity, commitment fee percentage	0.40%
Line of credit facility, current borrowing capacity	223,995,000	223,936,000
Line of credit facility, amount outstanding	180,000,000	140,000,000
Line of credit facility, remaining borrowing capacity	43,995,000	83,936,000
Amount of letters of credit outstanding	1,000,000
Weighted average interest rate	2.50%	2.30%
Interest rate at period end	3.10%	3.00%
Loan processing fee		1,200,000
Minimum interest coverage ratio	4.00
Line of credit facility, availability required to pay dividends	15,000,000
NACoal | Maximum
Line of Credit Facility [Line Items]
Maximum EBITDA ratio	3.50
NACoal | Minimum
Line of Credit Facility [Line Items]
Maximum EBITDA ratio	3.00
Base Rate | HBB | US Dollar
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.00%
Base Rate | HBB | Canadian Dollar
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.00%
Base Rate | KC
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.00%
Base Rate | NACoal
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.25%
LIBOR Rate | HBB | US Dollar
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.50%
LIBOR Rate | HBB | Canadian Dollar
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.50%
LIBOR Rate | KC
Line of Credit Facility [Line Items]
Basis spread on variable rate	2.00%
LIBOR Rate | NACoal
Line of Credit Facility [Line Items]
Basis spread on variable rate	2.25%
Private Placement Notes | NACoal
Line of Credit Facility [Line Items]
Long-term debt	0	6,429,000
Note Payable to Coteau | NACoal
Line of Credit Facility [Line Items]
Interest rate at period end	0.38%
Debt instrument, amount outstanding	$ 2,800,000