Represents the average silver price realized during the period.

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The minimum average realized silver price per ounce that must be met for the silver-price-linked component of dividends to be declared.

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Represents the common stock aggregate offering price.

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Represents the cumulative number of shares that have been repurchased up to a certain date.

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No definition available.

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Aggregate dividends declared during the period for each share of common stock outstanding.

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Amount of paid and unpaid common stock dividends declared with the form of settlement in cash, stock and payment-in-kind (PIK).

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The amount of cash paid for brokerage fees during the current period. This element is intended to represent the brokerage fees paid by and between financial industry participants.

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Amount of cash outflow to satisfy an employee's income tax withholding obligation as part of a net-share settlement of a share-based award.

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Number of share instruments newly issued under a share-based compensation plan.

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Price of a single share of a number of saleable stocks of a company.

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For net-share settlement of share-based awards when the employer settles employees' income tax withholding obligations, this element represents the number of shares the employees use to repay the employer.

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Number of new stock issued during the period.

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Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

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The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

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The remaining number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

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Total cost of shares repurchased divided by the total number of shares repurchased.

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Note 8 - Stockholders' Equity (Details Textual) $ / shares in Units, $ in Millions		1 Months Ended	3 Months Ended		25 Months Ended	71 Months Ended
	May 09, 2018 USD ($) $ / shares	Mar. 31, 2018 USD ($) $ / item shares	Mar. 31, 2018 USD ($) $ / shares $ / item shares	Mar. 31, 2017 USD ($) $ / shares shares	Mar. 31, 2018 USD ($) $ / item shares	Mar. 31, 2018 $ / shares $ / item shares	May 08, 2018 $ / shares	Feb. 23, 2016 USD ($)	May 08, 2012 shares
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period \| shares		1,237,369
Allocated Share-based Compensation Expense, Total \| $		$ 4.9	$ 1.1	$ 1.3
Shares Paid for Tax Withholding for Share Based Compensation \| shares			335,349	154,933
Payments Related to Tax Withholding for Share-based Compensation \| $			$ 1.2	$ 0.7
Treasury Stock Acquired, Average Cost Per Share \| $ / shares			$ 3.65	$ 4.67
Average Realized Silver Price \| $ / item			16.84
Average Realized Silver Price, Minimum Dividend, Threshold \| $ / item		30	30		30	30
Stock Issued During Period, Shares, New Issues \| shares			0		4,608,847
Stock Issued During Period, Value, New Issues \| $					$ 17.7
Payments for Brokerage Fees \| $					$ 0.4
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	934,100
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased \| shares		19,100,000	19,100,000		19,100,000	19,100,000
Subsequent Event [Member]
Common Stock, Dividends, Per Share, Declared \| $ / shares	$ 0.0025
Dividends, Common Stock, Total \| $	$ 1.0
Share Price \| $ / shares							$ 3.97
Subsequent Event [Member] \| Common Stock Repurchase Program [Member]
Share Price \| $ / shares							$ 3.97
Minimum [Member]
Common Stock, Dividends, Per Share, Declared \| $ / shares			$ 0.01
Maximum [Member]
Common Stock, Aggregate Offering Price \| $								$ 75.0