Property, Plant and Equipment, Net (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 T	Dec. 31, 2011 T	Dec. 31, 2010
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	$ 294.4	$ 213.2
Less allowances for depreciation, depletion and amortization	111.4	106.0
Property, plant and equipment, net	183.0	107.2
Depreciation, depletion and amortization	15.2	14.3	14.8
Proved and probable reserves (tons)	1,200,000,000	1,300,000,000
Coal lands and real estate
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	67.8	36.9
Plant and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	226.6	176.3
NACoal | Coal lands and real estate
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	67.6	36.7
NACoal | Plant and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	149.9	99.7
HBB | Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Tangible asset impairment charges		1.3
HBB | Coal lands and real estate
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	0.2	0.2
HBB | Plant and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	42.9	41.0
KC
Property, Plant and Equipment [Line Items]
Tangible asset impairment charges	0.7
KC | Plant and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	29.5	29.1
NACCO and Other | Plant and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	$ 4.3	$ 6.5