Note 6. Business Segments (Detail) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012
Number of Reportable Segments		2
Estimated Cost on Projects Based on MSHA Plan		$ 62,000,000
Noncapital Costs		25,000,000
Other Nonrecurring Expense	6,114,000	18,745,000
Lucky Friday [Member] | Depreciation Depletion and Amortization [Member]
Other Nonrecurring Expense	6,100,000	4,600,000
Lucky Friday [Member]
Other Nonrecurring Expense	18,700,000	1,500,000
Cost to Remove Loose Cementitious Material [Member]
Estimated Cost on Projects Based on MSHA Plan		29,000,000
Cost for Shaft Improvements [Member]
Estimated Cost on Projects Based on MSHA Plan		$ 33,000,000