Note 8 - Shareholders' Equity (Details Textual)		1 Months Ended	3 Months Ended
	May. 04, 2016 USD ($) $ / shares	Mar. 31, 2016 USD ($) $ / oz shares	Mar. 31, 2016 USD ($) $ / shares $ / oz shares	Mar. 31, 2015 USD ($) $ / shares shares	May. 03, 2016 $ / shares	Feb. 23, 2016 USD ($)	Dec. 31, 2015 $ / shares shares	May. 08, 2012 shares
Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period | shares			2,335,196
Allocated Share-based Compensation Expense | $			$ 5,500,000
Restricted Stock Units (RSUs) [Member]
Allocated Share-based Compensation Expense | $			$ 1,200,000	$ 1,100,000
Satisfy Withholding Obligations [Member]
Shares Paid for Tax Withholding for Share Based Compensation | shares			532,157	284,243
Payments Related to Tax Withholding for Share-based Compensation | $			$ 1,300,000	$ 900,000
Treasury Stock Acquired, Average Cost Per Share | $ / shares			$ 2.36	$ 3.31
Minimum [Member]
Common Stock, Dividends, Per Share, Declared | $ / shares			0.01
Maximum [Member]
Common Stock, Aggregate Offering Price | $						$ 75,000,000
Subsequent Event [Member]
Common Stock, Dividends, Per Share, Declared | $ / shares	$ 0.0025
Dividends, Common Stock | $	$ 1,000,000
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
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased | shares		19,100,000	19,100,000
Average Realized Silver Price | $			$ 14.93
Average Realized Silver Price Minimum Dividend Threshold | $ / oz		30	30
Stock Issued During Period, Shares, New Issues | shares		737,275
Stock Issued During Period, Value, New Issues | $		$ 2,100,000
Payments for Brokerage Fees | $		$ 42,000
Share Price | $ / shares					$ 4.05
Class of Warrant or Right, Outstanding | shares		0	0				2,249,550
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares							0.1622
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares							$ 6.17