Current and Long-Term Financing (Debt Schedule) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Total outstanding borrowings:	$ 149.7	$ 67.0
Capital lease obligations and other term loans:	15.2	61.9
Private Placement Notes — NACoal	166.0	145.3
Total debt outstanding	177.7	148.2
Current portion of borrowings outstanding:	42.3	73.7
Long-term portion of borrowings outstanding:	135.4	74.5
Total available borrowings, net of limitations, under revolving credit agreements:	287.8	264.0
Unused revolving credit agreements:	138.1	197.0
NACoal
Debt Instrument [Line Items]
Total outstanding borrowings:	110.0	67.0
Capital lease obligations and other term loans:	15.2	7.7
Current portion of borrowings outstanding:	29.6	73.7
Long-term portion of borrowings outstanding:	108.4	20.3
Total available borrowings, net of limitations, under revolving credit agreements:	148.8	148.8
Unused revolving credit agreements:	38.8	81.8
Weighted average stated interest rate on total borrowings:	2.40%	2.80%
Weighted average effective interest rate on total borrowings (including interest rate swap agreements):	2.40%	2.80%
HBB
Debt Instrument [Line Items]
Total outstanding borrowings:	39.7	0
Capital lease obligations and other term loans:	0	54.2
Current portion of borrowings outstanding:	12.7	0
Long-term portion of borrowings outstanding:	27.0	54.2
Total available borrowings, net of limitations, under revolving credit agreements:	112.0	88.2
Unused revolving credit agreements:	72.3	88.2
Weighted average stated interest rate on total borrowings:	1.90%	2.80%
Weighted average effective interest rate on total borrowings (including interest rate swap agreements):	4.30%	5.70%
KC
Debt Instrument [Line Items]
Total outstanding borrowings:	0
Total available borrowings, net of limitations, under revolving credit agreements:	27.0	27.0
Unused revolving credit agreements:	27.0	27.0
Private Placement Notes | NACoal
Debt Instrument [Line Items]
Private Placement Notes — NACoal	$ 12.8	$ 19.3
Weighted average stated interest rate on total borrowings:	6.08%