Note 8 - Stockholders' Equity (Details Textual)		1 Months Ended	3 Months Ended		13 Months Ended
	May 04, 2017 USD ($) $ / shares	Mar. 31, 2017 USD ($) $ / shares $ / oz shares	Mar. 31, 2017 USD ($) $ / shares $ / oz shares	Mar. 31, 2016 USD ($) $ / shares shares	Mar. 31, 2017 USD ($) $ / shares $ / oz shares	Feb. 23, 2016 USD ($)	May 08, 2012 shares
Shares Paid for Tax Withholding for Share Based Compensation | shares			154,933	532,157
Payments Related to Tax Withholding for Share-based Compensation			$ 700,000	$ 1,300,000
Treasury Stock Acquired, Average Cost Per Share | $ / shares			$ 4.67	$ 2.36
Average Realized Silver Price			$ 17.90
Average Realized Silver Price Minimum Dividend Threshold | $ / oz		30	30		30
Stock Issued During Period, Shares, New Issues | shares					2,780,087
Stock Issued During Period, Value, New Issues					$ 8,100,000
Payments for Brokerage Fees					$ 166,000
Common Stock Repurchase Program [Member]
Treasury Stock Acquired, Average Cost Per Share | $ / shares			$ 3.99
Stock Repurchase Program, Number of Shares Authorized to be Repurchased | shares							20,000,000
Cumulative Stock Repurchased | shares		934,100	934,100		934,100
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased | shares		19,100,000	19,100,000		19,100,000
Subsequent Event [Member]
Common Stock, Dividends, Per Share, Declared | $ / shares	$ 0.0025
Dividends, Common Stock	$ 1,000,000
Subsequent Event [Member] | Common Stock Repurchase Program [Member]
Share Price | $ / shares		$ 5.14	$ 5.14		$ 5.14
Minimum [Member]
Common Stock, Dividends, Per Share, Declared | $ / shares			$ 0.01
Maximum [Member]
Common Stock, Aggregate Offering Price						$ 75,000,000
Employees and Non-employee Directors [Member]
Allocated Share-based Compensation Expense			$ 1,300,000	$ 1,200,000
Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period | shares		641,406
Allocated Share-based Compensation Expense		$ 4,200,000