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Note 8 - Shareholders' Equity (Details Textual) $ / shares in Units, $ in Thousands |  | 1 Months Ended | 3 Months Ended | 6 Months Ended | 9 Months Ended | 65 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Nov. 07, 2017 USD ($) $ / shares | Jun. 30, 2017 USD ($) shares | Mar. 31, 2017 USD ($) shares | Sep. 30, 2017 $ / shares $ / oz $ / item shares | Sep. 30, 2016 $ / shares | Sep. 30, 2017 USD ($) $ / oz shares | Sep. 30, 2017 USD ($) $ / shares $ / oz shares | Sep. 30, 2016 USD ($) $ / shares shares | Sep. 30, 2017 $ / shares $ / oz shares | Nov. 03, 2017 $ / shares | Feb. 23, 2016 USD ($) | May 08, 2012 shares
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period | shares |  |  | 641,406 |  |  |  |  |  |  |  |  |
Allocated Share-based Compensation Expense | $ |  |  | $ 4,200 |  |  |  | $ 4,900 | $ 4,800 |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Measurement Period Used to Value Performance-based Awards |  | 3 years |  |  |  |  |  |  |  |  |  |
Shares Paid for Tax Withholding for Share Based Compensation | shares |  |  |  |  |  |  | 588,240 | 1,010,509 |  |  |  |
Payments Related to Tax Withholding for Share-based Compensation | $ |  |  |  |  |  |  | $ 3,000 | $ 3,500 |  |  |  |
Treasury Stock Acquired, Average Cost Per Share | $ / shares |  |  |  |  |  |  | $ 5.09 | $ 3.44 |  |  |  |
Common Stock, Dividends, Per Share, Declared | $ / shares |  |  |  | $ 0.0025 | $ 0.0025 |  | $ 0.0075 | $ 0.0075 |  |  |  |
Average Realized Silver Price | $ / item |  |  |  | 17.01 |  |  |  |  |  |  |  |
Average Realized Silver Price, Minimum Dividend, Threshold | $ / oz |  |  |  | 30 |  | 30 | 30 |  | 30 |  |  |
Stock Issued During Period, Shares, New Issues | shares |  |  |  |  |  | 1,828,760 | 4,608,847 |  |  |  |  |
Stock Issued During Period, Value, New Issues | $ |  |  |  |  |  | $ 9,600 | $ 17,700 |  |  |  |  |
Payments for Brokerage Fees | $ |  |  |  |  |  | $ 196 | $ 362 |  |  |  |  |
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 |  |  |
Treasury Stock, Shares, Acquired | shares |  |  |  |  |  |  | 0 |  |  |  |  |
Subsequent Event [Member] |  |  |  |  |  |  |  |  |  |  |  |
Common Stock, Dividends, Per Share, Declared | $ / shares | $ 0.0025 |  |  |  |  |  |  |  |  |  |  |
Dividends, Common Stock | $ | $ 1,000 |  |  |  |  |  |  |  |  |  |  |
Subsequent Event [Member] | Common Stock Repurchase Program [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share Price | $ / shares |  |  |  |  |  |  |  |  |  | $ 4.45 |  |
Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |
Common Stock, Dividends, Per Share, Declared | $ / shares |  |  |  |  |  |  | $ 0.01 |  |  |  |  |
Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |
Common Stock, Aggregate Offering Price | $ |  |  |  |  |  |  |  |  |  |  | $ 75,000 |
Restricted Stock Units (RSUs) Vesting in June 2018, 2019, and 2020 [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period | shares |  | 775,379 |  |  |  |  |  |  |  |  |  |
Restricted Stock Units (RSUs) Vesting in June 2018, 2019, and 2020 [Member] | Share-based Compensation Award, Tranche One [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage |  | 33.00% |  |  |  |  |  |  |  |  |  |
Restricted Stock Units (RSUs) Vesting in June 2018, 2019, and 2020 [Member] | Share-based Compensation Award, Tranche Two [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage |  | 33.00% |  |  |  |  |  |  |  |  |  |
Restricted Stock Units (RSUs) Vesting in June 2018, 2019, and 2020 [Member] | Share-based Compensation Award, Tranche Three [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage |  | 33.00% |  |  |  |  |  |  |  |  |  |
Restricted Stock Units (RSUs) Vesting in June 2018 and 2019 [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period | shares |  | 93,691 |  |  |  |  |  |  |  |  |  |
Restricted Stock Units (RSUs) Vesting in June 2018 and 2019 [Member] | Share-based Compensation Award, Tranche One [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage |  | 50.00% |  |  |  |  |  |  |  |  |  |
Restricted Stock Units (RSUs) Vesting in June 2018 and 2019 [Member] | Share-based Compensation Award, Tranche Two [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage |  | 50.00% |  |  |  |  |  |  |  |  |  |
Restricted Stock Units (RSUs) Vesting in June 2018 [Member] |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period | shares |  | 15,336 |  |  |  |  |  |  |  |  |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options | $ |  | $ 1,900 |  |  |  |  |  |  |  |  |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition |  | 1 year |  |  |  |  |  |  |  |  |  |
Restricted Stock Units (RSUs) Vesting in June 2019 [Member] |  |  |  |  |  |  |  |  |  |  |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options | $ |  | $ 1,800 |  |  |  |  |  |  |  |  |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition |  | 2 years |  |  |  |  |  |  |  |  |  |
Restricted Stock Units (RSUs) Vesting in June 2020 [Member] |  |  |  |  |  |  |  |  |  |  |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options | $ |  | $ 1,500 |  |  |  |  |  |  |  |  |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition |  | 3 years |  |  |  |  |  |  |  |  |  |
Performance Shares [Member] |  |  |  |  |  |  |  |  |  |  |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options | $ |  | $ 600 |  |  |  |  |  |  |  |  |  |
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition |  | 2 years 180 days |  |  |  |  |  |  |  |  |  |

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- Definition The minimum average realized silver price per ounce that must be met for the silver-price-linked component of dividends to be declared. + References No definition available. + Details
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- Definition Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition Number of share instruments newly issued under a share-based compensation plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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- Definition 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. + References No definition available. + Details
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