Note 6. Business Segments (Detail) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Number of Reportable Segments	2
Estimated Cost on Projects Based on MSHA Plan	$ 50,000,000
Noncapital Costs	17,500,000
Other Nonrecurring Expense	6,166,000
Depreciation, Depletion and Amortization	11,269,000	12,327,000
Lucky Friday [Member]
Depreciation, Depletion and Amortization	1,500,000
Cost to Remove Loose Cementitious Material [Member]
Estimated Cost on Projects Based on MSHA Plan	10,000,000
Cost for Shaft Improvements [Member]
Estimated Cost on Projects Based on MSHA Plan	20,000,000
Cost on Other Capital Projects [Member]
Estimated Cost on Projects Based on MSHA Plan	$ 20,000,000