Current and Long-Term Financing (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended					12 Months Ended													12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 HBB period	Dec. 31, 2011 HBB	Dec. 31, 2012 KC	Dec. 31, 2011 KC	Dec. 31, 2010 KC	Dec. 31, 2012 NACoal	Dec. 31, 2011 NACoal	Dec. 31, 2012 Base Rate KC	Dec. 31, 2012 Base Rate NACoal	Dec. 31, 2012 LIBOR Rate KC	Dec. 31, 2012 LIBOR Rate NACoal	Dec. 31, 2012 US Dollar Base Rate HBB	Dec. 31, 2012 US Dollar LIBOR Rate HBB	Dec. 31, 2012 Canadian Dollar Base Rate HBB	Dec. 31, 2012 Canadian Dollar LIBOR Rate HBB	Dec. 31, 2012 Private Placement Notes NACoal	Dec. 31, 2005 Private Placement Notes NACoal	Dec. 31, 2012 Note Payable to Coteau NACoal
Line of Credit Facility [Line Items]
Interest paid	$ 5.5	$ 8.5	$ 10.8
Interest capitalized	0	0	0.2
Line of credit facility, maximum borrowing capacity				115.0		30.0			150.0
Assets held as collateral				215.5		81.0
Basis spread on variable rate											1.00%	0.75%	2.00%	1.75%	0.00%	1.50%	0.00%	1.50%
Line of credit facility, unused capacity, commitment fee percentage				0.375%		0.375%			0.35%
Line of credit facility, current borrowing capacity	287.8	264.0		112.0	88.2	27.0	27.0		148.8	148.8
Line of credit facility, amount outstanding	149.7	67.0		39.7	0	0			110.0	67.0
Line of credit facility, remaining borrowing capacity	138.1	197.0		72.3	88.2	27.0	27.0		38.8	81.8
Dividend restriction from closing date				15.0		2.0
Dividend restriction mimimum credit facility amount				20.0
Dividend restriction number of fiscal periods				2
Dividend restriction period following closing date of credit facility				12 months		12 months
Dividend restriction credit facility excess availability requirement				25.0		7.5
Interest rate at period end				1.98%					1.95%												0.23%
Minimum fixed charge coverage ratio				1.0		1.1
Dividend restriction from closing date including minimum fixed charge coverage ratio						6.0
Dividend restriction credit facility excess availability requirement as defined within the agreement						15.0
Dividend payment restrictions schedule, description				(i) $15.0 million from the closing date of the HBB Facility through December 31, 2012, so long as HBB has excess availability, as defined in the HBB Facility, of at least $30.0 million; (ii) the greater of $20.0 million or excess cash flow from the most recently ended fiscal year in each of the two twelve-month periods following the closing date of the HBB Facility, so long as HBB has excess availability under the HBB Facility of not less than $25.0 million and maintains a minimum fixed charge coverage ratio of 1.0 to 1.0, as defined in the HBB Facility; and (iii) in such amounts as determined by HBB subsequent to the second anniversary of the closing date of the HBB Facility, so long as HBB has excess availability under the HBB Facility of not less than $25.0 million.		(i) $6.0 million in any twelve-month period, so long as KC has excess availability, as defined in the KC Facility, of at least $7.5 million after giving effect to such payment and maintaining a minimum fixed charge coverage ratio of 1.1 to 1.0, as defined in the KC Facility; (ii) $2.0 million in any twelve-month period, so long as KC has excess availability, as defined in the KC Facility, of at least $7.5 million after giving effect to such payment and (iii) in such amounts as determined by KC, so long as KC has excess availability under the KC Facility of $15.0 million after giving effect to such payment.
Loan processing fee				1.2		0.2	0	0.4	0.8
Amount of letters of credit outstanding									1.2
Maximum EBITDA ratio									3.0										3.5
Minimum interest coverage ratio									4.0
Line of credit facility, availability required to pay dividends				30.0					15.0
Face amount																				45.0
Periodic payment, principal																			6.4
Weighted average interest rate				1.90%	2.80%				2.40%	2.80%									6.08%
Debt instrument, amount outstanding																			$ 12.9		$ 3.5