Note 6. Business Segments (Detail) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Jun. 30, 2011
Number of Reportable Segments		2
Estimated Cost on Projects Based on MSHA Plan		$ 50,000,000
Noncapital Costs		26,000,000
Other Nonrecurring Expense	6,465,000	12,631,000
Depreciation, Depletion and Amortization		22,799,000	23,597,000
Lucky Friday [Member] | Depreciation Depletion and Amortization [Member]
Other Nonrecurring Expense	1,600,000
Depreciation, Depletion and Amortization		3,100,000
Lucky Friday [Member]
Other Nonrecurring Expense	6,400,000	12,600,000
Cost to Remove Loose Cementitious Material [Member]
Estimated Cost on Projects Based on MSHA Plan		26,000,000
Cost for Shaft Improvements [Member]
Estimated Cost on Projects Based on MSHA Plan		$ 24,000,000