Business Segments (Balance Sheets) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Total assets	$ 776.3	$ 1,808.7	$ 1,670.9
Depreciation, depletion and amortization	18.0	16.4	18.3
Capital expenditures	44.7	20.2	15.8
NACoal
Segment Reporting Information [Line Items]
Total assets	368.7	278.5	269.2
Depreciation, depletion and amortization	10.9	7.9	9.9
Capital expenditures	37.1	14.1	9.8
HBB
Segment Reporting Information [Line Items]
Total assets	215.5	201.5	251.7
Depreciation, depletion and amortization	3.1	4.9	3.6
Capital expenditures	3.2	3.7	2.2
KC
Segment Reporting Information [Line Items]
Total assets	84.0	89.0	86.6
Depreciation, depletion and amortization	3.6	3.1	3.5
Capital expenditures	3.9	2.3	2.7
NACCO and Other
Segment Reporting Information [Line Items]
Total assets	154.6	169.5	71.8
Depreciation, depletion and amortization	0.4	0.5	1.3
Capital expenditures	0.5	0.1	1.1
Discontinued Operations
Segment Reporting Information [Line Items]
Total assets	0	1,117.0	1,041.2
Eliminations
Segment Reporting Information [Line Items]
Total assets	$ (46.5)	$ (46.8)	$ (49.6)